BACKGROUND: Co-occurring mental health disorders are widespread among substance using adolescents. Severity of victimization may be an important factor in explaining co-occurrence of mental health problems among adolescents with substance misuse problems. PURPOSE: The purpose of this study was to evaluate whether severe victimization experiences were shared risk factors for internalizing only, externalizing only, and co-occurring internalizing and externalizing disorders among victimized substance-using adolescents. METHOD: Data for this cross-sectional study were obtained from a multisite research project. Adolescents, ages 11-18, participated in a comprehensive screening program for substance abuse at 106 Substance Abuse and Mental Health Services Administration (SAMHSA) Center for Substance Abuse Treatment (CSAT)-funded grantee sites throughout the United States. RESULTS: Longer duration/frequent victimization, more than one type of victimization, and recent victimization were related to co-occurring internalizing and externalizing disorders. Victimization by a trusted person, however, was only related to internalizing disorders. CONCLUSION: The findings show that some indicators of severe victimization experiences are shared risk factors for internalizing, for externalizing, and for co-occurring internalizing and externalizing problems, thus providing support for the common factors model of co-morbidity. These findings suggest that practitioners in substance abuse treatment must thoroughly assess for severe victimization experiences among adolescents presenting with co-occurring mental health issues. Treatment planning and interventions may focus on helping adolescents cope effectively with their victimization experiences and addressing their MH needs.