The goal of this study is to evaluate the efficacy of a brief early intervention (BEI) for reducing early alcohol and marijuana use in a group of 300 adolescents (age 12-16) with ADHD. All adolescents will receive the BEI based on the Teen Intervene program with the addition of enhanced decision making skills. Due to the existing support for the intervention and concern for randomizing families with adolescents at risk for worsening substance use outcomes into a control (no treatment) condition for one to two years, no control condition is used in the current design at the first level of intervention. Similarly, due to the time required to see a potential effect of the treatment (6 months post-brief intervention), a wait-list control condition was not considered.