PURPOSE: Alcohol and drug problems are associated with medical problems among adults. Research on the relationship of adolescent alcohol and drug use disorders to specific medical problems is less developed and focused on acute consequences. This study addresses gaps in the literature regarding medical comorbidities in adolescents with alcohol and drug use disorders. METHODS: This study compares the prevalence of medical conditions among 417 adolescent alcohol and drug treatment patients with 2082 demographically matched controls from the same managed care health plan and examines whether comparisons vary among substance-type subgroups. RESULTS: Approximately one-fourth of the comorbid conditions examined were more common among adolescent alcohol and drug patients than among matched controls, and several were highly costly conditions (e.g., asthma, injury). We also found that pain-related diagnoses, including headache and abdominal pain, were more prevalent among alcohol and drug patients. CONCLUSIONS: Our findings point to the importance of examining comorbid medical and chemical dependency in both adolescent primary care and specialty care. Moreover, optimal treatment of many common medical disorders may require identification, intervention, and treatment of a substance use problem.