Objective: To describe psychotropic treatment pattern and evaluate the association of socio-demographic factors and psychotropic combination therapy in children with ADHD and oppositional defiant disorder/conduct disorder (ODD/CD). Method: This is a cross-sectional drug utilization study based on Medicaid fee-for-service programs in 26 U.S. states (1999-2006). Children aged 4 to 18 with concomitant ADHD and ODD/CD were included. We calculated the prevalence of psychotropic drugs and used logistic regression to evaluate the role of socio-demographic factors in psychotropic combination therapy. Results: We identified 121,740 children with ADHD and ODD/CD (140,777 person-years). The period prevalence of "no psychotropic therapy," psychotropic monotherapy, and psychotropic dual therapy was 38.1%, 44.7%, and 9.0%, respectively. The most common drug class was stimulants. Whites, males, and children in foster care were more likely to use psychotropic combination therapy. State-level variation was observed. Conclusion: "No psychotropic therapy" and stimulants dominate treatment choices in children with ADHD and ODD/CD. Socio-demographic characteristics are associated with combination psychotropic therapy.