We investigated whether the correlates of family psychosocial characteristics among Japanese children with attention-deficit hyperactivity disorder (ADHD) differ according to the comorbid condition of oppositional defiant disorder (ODD) or conduct disorder (CD). Three groups of children (12 ADHD, 15 ADHD + ODD/CD, and 14 control) were compared on family psychosocial variables. Findings indicated that the interpersonal relationships in ADHD + ODD/CD children's family were more conflictive and less organized than those of the control. Mental health among mothers of ADHD + ODD/CD children was worse than those of ADHD and control children. Childhood ADHD symptoms of parents were the most severe among parents of ADHD + ODD/CD children. These results support the nosological distinction between ADHD comorbid with ODD and CD. The need for specific clinical intervention according to the comorbid condition is stressed.