The newly developed CBT for ADHD inattentive-type (ADHD-I) protocol is tested for feasibility and acceptability in a pilot study with a single group design. The study also evaluates measurements and recruiting possibilities, and effects of the intervention. Research hypotheses include: 1. There is a basis for recruiting ADHD-I patients for participation in an RCT at psychiatric outpatient units, 2. The measurements in the study are feasible and reasonable in regards to patient characteristics; that is, the patients are responding to the questionnaires as intended, 3. The CBT for ADHD-I intervention is feasible in terms of treatment completion, compliance to home assignments, and credibility and relevance, and is lacking of or involves a tolerable degree of adverse effects, and 4. The CBT for ADHD-I protocol reduces core symptoms of ADHD-I as well as symptoms of stress, depression, and anxiety, and improves quality of life.

Inclusion Criteria:

In addition to an ADHD inattentive-type diagnosis, inclusion criteria are:

1. 18 years or older,
2. intelligence quotient above 80-85, and
3. if on medication, it needs to be well-established since three months.

Exclusion Criteria:

1. autism spectrum disorder,
2. ongoing substance use disorder,
3. difficulties in compliance with medical or other treatment,
4. social and/or psychiatric problems to such an extent that it prevents focusing on treatment, or
5. ongoing cognitive-behavioral therapy.