ADD or ADHD? How they differ

Written and professionally reviewed by Felix Enghoff Klich, authorised psychologist
Last updated: September 2026

What is the difference between ADD and ADHD? The terms are often used as names for two different diagnoses, but professionally, ADD is today part of the ADHD diagnosis.

The most important difference concerns how the symptoms show. In what is often called ADD, attention difficulties are most prominent, while hyperactivity and impulsivity are less obvious. In other forms of ADHD, hyperactivity and impulsivity can play a bigger role.

ADD is still widely used in everyday language. Professionally, one typically speaks of ADHD, predominantly inattentive presentation.

What is ADHD?

ADHD stands for Attention Deficit Hyperactivity Disorder and is a neurodevelopmental disorder.

ADHD can affect, among other things, the ability to:

• sustain attention
• regulate activity level and impulses
• plan and organise
• get started on and finish tasks
• keep track of things
• manage time and appointments

Symptoms of ADHD begin in childhood but can continue through adolescence and into adulthood.

How ADHD shows can also change over a lifetime. In adults, for example, hyperactivity does not have to show as an obviously high level of physical activity. Instead, it can be experienced as inner restlessness, agitation, racing thoughts or difficulty switching off.

Overall, ADHD is associated with symptoms in three areas:

• Attention difficulties
• Hyperactivity
• Impulsivity

How much each area dominates varies from person to person.

What is ADD?

ADD stands for Attention Deficit Disorder. The term is still often used about people who have significant difficulties with attention and concentration without obvious hyperactivity.

Professionally, ADD is today regarded as ADHD, predominantly inattentive presentation rather than as a separate diagnosis.

People with this form of ADHD can therefore have significant difficulties, even though they do not seem hyperactive or impulsive to others.

Typical symptoms of ADD

Symptoms of ADD particularly concern attention, concentration, organisation and the ability to turn intentions into action.

You may, for example, have difficulty:

• maintaining concentration
• getting started on tasks
• finishing tasks
• planning and prioritising
• keeping an overview and structure
• remembering appointments and practical chores
• following longer conversations or lectures
• keeping track of time
• filtering out irrelevant impressions
• staying focused on tasks that feel monotonous or demanding

Some also experience mental fatigue, daydreaming, racing thoughts or difficulty turning thoughts and plans into action.

From the outside, the person may at the same time appear calm, quiet or thoughtful. The difficulties can therefore be less visible to others.

What is the difference between ADD and ADHD?

The difference between ADD and ADHD is first and foremost about how prominent hyperactivity and impulsivity are.

In ADD, attention difficulties are typically the most prominent. The person can have significant problems with concentration, structure, overview and getting started, but without being obviously physically hyperactive.

In ADHD with hyperactive and impulsive symptoms, there may to a greater extent be restlessness, a high activity level, impulsive actions or difficulty waiting and holding back.

However, the difference is not always clear.

A person with the inattentive presentation may, for example, well experience inner restlessness or impulsivity, even if it is not very visible to others. Conversely, adults with ADHD are not necessarily physically hyperactive.

Is ADD a diagnosis?

ADD is a term that is still widely used, but in modern diagnostic language the symptom picture is regarded as part of ADHD.

Broadly, one can distinguish between:

• ADHD, predominantly inattentive presentation
• ADHD, predominantly hyperactive-impulsive presentation
• ADHD, combined presentation

When a person says they have ADD, it will therefore typically correspond to ADHD, predominantly inattentive presentation.

ADD and ADHD in adults

ADD and ADHD in adults can look different than in children.

Demands for independence, planning and organisation typically increase in adulthood. Difficulties that could previously be compensated for may therefore become more apparent in connection with education, work, family life or other greater demands.

In adults, ADD or ADHD can show, among other things, as:

• repeatedly missed deadlines
• problems with sense of time
• frequent lateness
• many started but unfinished tasks
• forgetfulness
• problems with post, finances or appointments
• difficulty prioritising between tasks
• quick mental fatigue
• fluctuating motivation and work effort
• difficulty regulating emotions and reactions

Some adults also describe being able to concentrate very intensely on certain activities, while other tasks are very hard to get started on.

This does not necessarily mean that the person does not have attention difficulties. Attention can be strongly affected by, among other things, interest, motivation, structure and the level of stimulation.

ADD can be less visible

For some people with the inattentive presentation of ADHD, the diagnosis is only made in adulthood.

One possible explanation is that the difficulties do not necessarily cause problems for those around them.

A child who sits still, daydreams or loses concentration is, for example, not necessarily noticed in the same way as a child who is physically restless and disrupts lessons.

Some have also developed extensive strategies throughout life to compensate for their difficulties.

They may, for example:

• spend a very long time preparing
• check their work repeatedly
• be very dependent on calendars, lists and fixed routines
• compensate through perfectionism
• work longer than others to achieve the same result
• depend on help and structure from those around them

A person can therefore appear to function well on the outside, while at the same time spending a lot of energy making everyday life work.

Why are some people only diagnosed with ADHD as adults?

An ADHD diagnosis in adulthood does not mean that ADHD first arose in adulthood.

ADHD is a developmental disorder. In an ADHD assessment, it is therefore important to examine whether relevant symptoms and difficulties can also be recognised from childhood.

For some, the difficulties only become apparent when demands for independence increase.

This can happen, for example, in connection with:

• upper secondary school or university
• a job with more responsibility
• moving away from home
• family life and children
• several simultaneous work and everyday tasks

The structure previously provided by parents, school or fixed routines may have made the symptoms less apparent.

How does an assessment for ADD or ADHD work?

A thorough assessment for ADD or ADHD is not based on the result of a single test.

The assessment typically involves an overall evaluation of symptoms, developmental history and level of functioning.

There will be a focus on, among other things:

• current symptoms
• symptoms in childhood
• schooling and education
• working life
• relationships and family life
• organisation and managing everyday life
• mental and physical health

Information from childhood can be particularly relevant. This may, for example, be information from a parent or another person who knew the person early in life. School reports and previous medical records can also be included.

Other causes of concentration problems

Concentration problems do not necessarily mean that you have ADD or ADHD.

Problems with concentration, memory, energy and overview can also occur in connection with, among other things:

• stress and prolonged strain
• anxiety
• depression
• sleep problems
• autism
• trauma reactions
• substance use
• medication
• various physical illnesses

An ADHD assessment is therefore not only about examining whether the symptoms of ADHD are present, but also about assessing whether there are other or additional explanations for the difficulties.

How are ADD and ADHD treated?

Treatment of ADHD is planned individually based on the person's symptoms, level of functioning and needs.

Treatment may include, among other things:

• psychoeducation and knowledge about ADHD
• concrete strategies for structure and planning
• adjusting demands and surroundings
• psychotherapeutic treatment
• medical treatment following a medical assessment
• treatment of co-occurring mental health difficulties

There is therefore no single treatment that suits everyone with ADD or ADHD.

The goal is to reduce the difficulties that affect everyday life and at the same time develop strategies that suit the individual.

When should you seek help?

Most people occasionally feel unfocused, forgetful or restless. That does not in itself mean that you have ADHD.

It may be relevant to seek a professional assessment if the difficulties have been present for a long time, can be recognised from earlier in life and significantly affect your functioning.

This may, for example, be problems in relation to:

• work
• education
• relationships
• family life
• finances
• practical everyday tasks

A thorough assessment can help clarify whether the difficulties are due to ADHD or whether they are better understood in terms of other factors.

Also read: ADHD symptoms in adults, DIVA-5 in the ADHD assessment and ADHD, anxiety and depression.

Frequently asked questions about ADD and ADHD

What is the biggest difference between ADD and ADHD?

The main difference is the degree of hyperactivity and impulsivity. In what is often called ADD, attention difficulties are most prominent, while hyperactivity and impulsivity are typically less obvious.

Is ADD a milder form of ADHD?

No, not necessarily. People with predominantly inattentive ADHD can have significant difficulties in everyday life, even though the symptoms are less visible to others.

What are typical signs of ADD in adults?

Typical signs can be problems with concentration, structure, sense of time, getting started, forgetfulness and finishing tasks. Some also experience mental fatigue, daydreaming or racing thoughts.

Can you have ADD and be restless?

Yes. A person can experience significant inner restlessness without appearing physically hyperactive. The line between the different ADHD presentations is therefore not always sharp.

Can you develop ADD as an adult?

ADHD does not first arise in adulthood. The symptoms must be traceable back to childhood, but for some the difficulties are only identified or diagnosed in adulthood.

How do I know if I have ADD or ADHD?

This cannot be determined reliably from an online self-test or individual symptoms. An ADHD diagnosis requires an overall professional assessment of symptoms, developmental history, level of functioning and possible alternative explanations.

Sources

• Sundhed.dk, Patienthåndbogen: ADHD, oversigt
• Sundhed.dk, Patienthåndbogen: ADHD hos voksne
• Sundhed.dk, Lægehåndbogen: Hyperkinetiske forstyrrelser/ADHD