OBJECTIVE To investigate the relative importance of ADHD symptoms, mood instability, and antisocial personality disorder traits in predicting self-reported offending. METHODS A total of 295 Icelandic students completed two scales of offending behavior and measures of ADHD symptoms, mood instability, and antisocial personality traits. RESULTS Self-reported offending from the two independent scales correlated significantly with ADHD symptoms, mood instability, and antisocial personality traits with medium to large effect size. Multiple regressions showed that ADHD symptoms contributed to the two outcome measures beyond that of age and gender with a medium effect size. The ADHD effects were only partly mediated by mood instability and antisocial personality traits for general offending but were almost completely mediated by the more reactive measure of antisocial behavior. CONCLUSIONS ADHD appears to be a potential risk factor for general offending in its own right irrespective of the presence of comorbidity, whereas mood instability is more important with regard to reactive behavior.