We report on the development of a German self-rating behaviour questionnaire (ADHD-SR) and diagnostic checklist (ADHD-DC) for the diagnosis of attention-deficit/hyperactivity disorder in adults according to DSM IV and ICD 10 research criteria. When comparing self-rating with expert rating, we found good concordance measured by intraclass coefficients on the level of single symptoms and syndrome scores. High retest reliability of the ADHD-SR demonstrated the ability to assess time-stable behaviour traits. Evaluation of the psychometric properties revealed good internal consistency and adequate convergent and divergent validity measured by the "big five" derived from the NEO-FFI and the constructs impulsivity, venturesomeness, and empathy of Eysenck's impulsiveness questionnaire. We detected a remarkable correlation with the Wender Utah Rating Scale, which targets the detection of childhood ADHD symptoms. Diagnostic sensitivity for different cutoff points was calculated by ROC analysis at 65--88%. Specificity was 67% to 92%.