ADHD is a serious risk factor for co-occurring psychiatric disorders and negative psychosocial consequences in adulthood. Previous trials on psychotherapeutic concepts for adult ADHD are based on behavioural (cognitive behavioural and dialectical behavioural) psychotherapeutic approaches and showed significant effects. The aim of our study group (COMPAS) is to carry out a first randomized and controlled multicentre study to evaluate the effects of a disorder tailored psychotherapy in adult ADHD compared to clinical management in combination with psychopharmacological treatment or placebo. A total of 448 adults with ADHD according to DSM-IV will be treated at seven university sites in Germany. In a four-arm design, patients are randomized to a manualized dialectical behavioural therapy (DBT) based group programme plus methylphenidate or placebo or clinical management plus methylphenidate or placebo with weekly sessions in the first 12 weeks and monthly sessions thereafter. Therapists are graduated psychologists or physicians. Treatment integrity is established by independent supervision. Primary endpoint (ADHD symptoms measured by the Conners Adult Rating Scale) is rated by interviewers blind to the treatment allocation. Intention-to-treat analysis will be performed within a linear regression model (Current Controlled Trials ISRCTN54096201). The trial is funded by the German Federal Ministry of Research and Education (01GV0606) and is part of the German network for the treatment of ADHD in children and adults (ADHD-NET).