BACKGROUND The purpose of this study was to investigate the differences between DSM-III-R Axis I and II psychiatric diagnoses in hospitalized adolescents with and without conduct disorder. The spectrum of psychopathology associated with conduct disorder, especially personality disorder symptoms and diagnoses, remains largely unexplored. METHODS Twenty-five inpatients were evaluated using the Diagnostic Interview for Children and Adolescents, Adolescent Version (DICA-R-A); the Schedule for Affective Disorders and Schizophrenia for School-Age Children, Epidemiologic Version (K-SADS-E) (panic disorder and agoraphobia only); and the Structured Interview for DSM-III-R Personality Disorders (SIDP-R). RESULTS Fifty-two percent met criteria for conduct disorder, and the majority of these had comorbid substance abuse, attention-deficit hyperactivity disorder, and major depression. The diagnosis of conduct disorder was also associated with fulfilling criteria for multiple Axis II personality disorders, particularly passive aggressive and histrionic. Nearly three personality disorders per subject were found in those with conduct disorder, while those without conduct disorder averaged just over one personality disorder. There was a trend for female subjects with conduct disorders to have more frequent and varied personality disorder diagnoses. For the entire sample, males were significantly more likely to have conduct disorder, and females were significantly more likely to have borderline personality disorder. CONCLUSIONS These findings support conduct disorder as a multifaceted illness composed of diverse Axis I and II characteristics. Long-term follow-up studies are needed to determine the outcome of personality disorder diagnoses made in adolescents with and without conduct disorder.