The validity of self-report measurement varies widely according to the type of behaviour investigated. For behaviour of overactivity and inattention, adolescents seem to underestimate their problems. Well validated instruments for self-report of attention deficit and hyperactivity disorder (ADHD) are lacking yet, and research on ADHD beyond childhood relies quite heavily on self-report. In this study, an attempt is made to validate an adolescent interview scale for DSM-based ADHD symptoms. Results show that the measure has a high inter-rater reliability and is a good predictor of general outcome. However, adolescents do not validly report on symptoms specifically of ADHD. Possible implications for research and clinical practice are formulated.