Objective: Little is known about the risks and characteristics of attention-deficit/hyperactivity disorder (ADHD) patients who misuse or divert their stimulant medications. As part of a 10-year longitudinal study of youths with ADHD, the authors evaluated medication diversion or misuse at the last follow-up period. Method: Structured psychiatric interviews for diagnosis and a self-report questionnaire regarding medication use in medicated subjects with ADHD compared with controls without ADHD receiving psychotropics for non-ADHD treatment were employed. Results: Of 98 subjects receiving psychotropic medications (mean age of 20.8 plus or minus 5 years), 55 (56%) were ADHD subjects and 43 (44%) were controls receiving medications for other purposes. The authors found that 11% of the ADHD group reported selling their medications compared with no subjects in the control group (z = 0.00, p less than 0.05). An additional 22% of the ADHD group reported misusing their medications compared with 5% of the control subjects (z = 1.7 p = 0.09) and that those with conduct or substance use disorders accounted for the misuse and diversion. A minority of subjects reported escalating their doses and concomitant use with alcohol and drugs. Conclusions: The data indicate that the majority of ADHD individuals, particularly those without conduct or substance use disorders, use their medications appropriately. The authors' findings also highlight the need to monitor medication use in ADHD individuals with conduct and/or substance use disorders and to carefully select agents with a low likelihood of diversion or misuse in this group. (Contains 1 table.)