The objective of this article is to review literature about the effects of stimulant therapy on substance use disorders and the potential for misuse and diversion of stimulants. We reviewed published literature relevant to these objectives, and studies were selected if they were published or accepted for publication in peer-reviewed journals. Prospective longitudinal studies show that attention-deficit/hyperactivity disorder (ADHD) is a risk factor for subsequent substance use disorders. These studies also suggest that ADHD pharmacotherapy in childhood reduces the risk for substance use disorders. Misuse and diversion of prescribed stimulants occur among a minority of ADHD patients, especially those with conduct or substance use disorders. Long-acting stimulants may be less likely to be misused or diverted.