 Subjects must 1 be between the ages of 13 and 19, with a parent or legal guardian available to complete parental assessments for minors; 2 meet DSM-IV diagnostic criteria for ADHD on the K-SADS-PL; 3 Schedule for Affective Disorders and Schizophrenia score or 22 on the DSM-IV ADHD symptom checklist; 4 meet DSM-IV criteria for nicotine dependence andor cut off score of 3 on modified Fagerstrom; 5 meet DSM-IV criteria for cannabis abuse or dependence on the Kiddie-Sads-Present and Lifetime K-SADS-PL; 6 have used marijuana at least 5 of the past 30 days; 7 have used nicotine at least 15 days out of the past 30 days; 8 be medically healthy; 9 use of effective birth control method if female and sexually active. 