This study focused on the personality characteristics associated with Attention-deficit/Hyperactivity disorder (ADHD) in a longitudinal sample of youth, with a particular focus on differences between those with and without persisting ADHD symptoms. Participants with ADHD (n = 90) were initially evaluated when they were 7-11 years old, and re-assessed at 16-22 years of age. Matched control subjects (n = 80) were recruited at the time of the follow-up evaluation. At follow-up, the Kiddie-SADS-PL, a semi-structured psychiatric interview, and the NEO-PI, a self-report personality inventory, were administered. Data were analyzed using multivariate analyses of variance (MANOVA). Results indicate that childhood ADHD is associated with lower scores on the NEO Conscientiousness subscale in adolescents/young adults--irrespective of the degree of ADHD persistence. In contrast, ratings of Neuroticism and Agreeableness appear to be more closely linked to adolescent status; those with persisting symptoms only exhibited increased Neuroticism and decreased Agreeableness. These results suggest that ADHD, and the degree to which symptoms persist into adolescence, may be closely linked to personality structure.