In this study 30 adolescents (ages 11-15) will be identified who have Attention Deficit Disorder and are at risk for alcohol and substance use problems. We propose to treat their Attention Deficit Hyperactivity Disorder with Vyvanse in the hope that it may prevent ADHD from promoting the development of alcohol and substance abuse problems. Our main goal is to see if we can identify children who are at risk because they have an older sibling who already has a substance abuse problem and Attention Deficit Hyperactivity Disorder. This is dubbed "the younger sibling design." Families will be recruited via contacts in adolescent substance abuse treatment centers (e.g. Phoenix House, Odyssey House). Participating substance abuse treatment centers will inform families of our study. We will conduct two phone screens followed by an in person evaluation to determine eligibility. Relevant information includes family history with special emphasis on the growth and development of both children, as well as the results of a comprehensive clinical evaluation of the younger child. Subjects will therefore be the younger siblings of substance abusers in which both sibs have ADHD but only the older sib uses drugs or alcohol regularly. All subjects will receive active medication and all will be assessed weekly for the first three months of the study and monthly for three months thereafter. The assessments will focus on ADHD symptoms, substance use, and overall adolescent problem behaviors.