Objective: To study the correlation between symptoms of ADHD in adults, obtained with different methods and from different sources. Method: Information was obtained from 120 adults with ADHD, their partners, and their parents, using the ADHD Rating Scale, the Conners' Adult ADHD Rating Scales (CAARS), the Brown Attention-Deficit Disorder Scale (BADDS), and the structured interview Diagnostic Interview Schedule-IV, section L (DIS-L). Results: All self-report rating scales can be used to assess ADHD symptoms in clinical samples of adults. The BADDS and the ADHD Rating Scale proved best in predicting the clinical diagnosis. The DSM-IV factors, originally developed for children, achieve lower patient-informant agreement than the other factors. Conclusion: Adults with ADHD appear to be the best informants with regard to their symptoms but tend to underreport the severity of their symptoms. Informant report may be used to get additional information on symptoms and impairment. (J. of Att. Dis. 2008; 11(4) 445-458).