Objective: To assess the efficacy of cognitive behavioral therapy (CBT) for managing adolescent ADHD. Method: A total of 68 adolescents with ADHD and associated psychiatric comorbidities completed a manualized CBT treatment protocol. The intervention used in the study was a downward extension of the Safren et al. program for adults with ADHD who have symptoms unresolved by medication. Outcome variables consisted of narrow band (ADHD) and broadband (e.g., mood, anxiety, conduct) symptom measures (Behavior Assessment System for Children–2nd edition and ADHD–Rating Scales) as well as functioning measures (parent/teacher ratings and several ecologically real-world measures). Results: Treatment effects emerged on the medication dosage, parent rating of pharmacotherapy adherence, adolescent self-report of personal adjustment (e.g., self-esteem), parent and teacher ratings of inattentive symptoms, school attendance, school tardiness, parent report of peer, family and academic functioning and teacher report of adolescent relationship with teacher, academic progress, and adolescent self-esteem. Adolescents with ADHD with oppositional defiant disorder were rated by parents and teachers as benefiting less from the CBT intervention. Adolescents with ADHD and comorbid anxiety/depression were rated by parents and teachers as benefiting more from the CBT intervention. Conclusion: A downward extension of an empirically validated adult ADHD CBT protocol can benefit some adolescents with ADHD.