This study examined social problems at school and relationships with peers, siblings, mothers, and fathers among children with ADHD only (n = 41), ODD only (n = 14), ADHD + ODD (n = 47), and normal controls (n = 204) from a school-based sample of 2,463 first to ninth graders in Taiwan. ADHD and ODD symptoms were determined by teacher and mother reports on the Conners' Rating Scales and social adjustment problems were assessed by mother reports on the Social Adjustment Inventory for Children and Adolescents. Results indicated that relative to normal controls, children with ADHD + ODD displayed greater levels of social adjustment problems across domains (i.e., school, peers, siblings, and parents) while children with ADHD were significantly more impaired only in social adjustment at schools and children with ODD were more impaired only in social adjustment at home. Some similarities and differences in our findings, in relation to the Western literature, were discussed.