The objective of this study was to compare the efficacy of cognitive behavioral therapy (CBT) versus psychoeducational therapy (PET) for adolescent substance abusers. Eighty-eight consecutively referred predominantly dually diagnosed adolescents were randomized to one of two eight-week, outpatient group psychotherapy conditions. Drug urinalysis and the Teen-Addiction Severity Index (T-ASI) were used as outcome measurements. Treatment completion rate was 86%, follow-up location rate was 95%, and rates of posttreatment at 3- and 9-month follow-up evaluation were 80% and 65%, respectively. Comorbid conduct disorder was significantly associated with treatment noncompletion and reduced follow-up rate. CBT subjects exhibited significantly lower rates of positive urinalysis than did PET subjects for older youth and male subjects at 3-month follow-up evaluation. Most T-ASI subscales indicated sound improvement from baseline to 3- and 9-month follow-up evaluation across conditions. Reduction in substance use was achieved regardless of treatment conditions. Replication of these findings, continued exploration of potential matching effects of conduct disorder, age, and gender to singular or integrative treatment modalities, and exploration of aftercare programs for the maintenance or enhancement of treatment gains are warranted.