The prevalence of substance abuse and coexisting DSM-III psychiatric disorders was evaluated in 111 juvenile offenders. As expected, a high rate of conduct disorder (91%) was present in both substance abusing and nonsubstance abusing juvenile offenders. However, significantly higher rates of attention deficit disorder and aggressive subtype of conduct disorder were present in those offenders who abused drugs and alcohol (54%). Excluding all conduct and oppositional disorder diagnoses, 39% of substance abusers versus 14% of the nonsubstance abusers demonstrated comorbid psychiatric diagnoses. These findings suggest that careful psychiatric evaluation of juvenile substance abusers may be necessary to optimize treatment planning.