Background: Children with attention-deficit/hyperactivity disorder (ADHD) are at risk for the development of comorbid conduct disorder (CD) and depression. The current study examined potential psychosocial risk factors for CD and depression in a clinic-based sample of 203 boys (aged 6-10 years) with ADHD. Methods: The boys and their mothers participated in an evaluation that involved assessments of cognitive, behavioral, academic, and family functioning. Potential predictors of CD and depression involved four domains: parenting behaviors, family environment, academic/cognitive functioning, and peer relations. ADHD groups were defined using mother- and teacher-report of DSM-IV symptoms. Mother-ratings of DSM-IV symptoms were obtained for a subsample of 91 boys approximately 5 years after the initial assessment. Results: For both mother- and teacher-defined ADHD groups, social problems were related to depression symptoms; hostile, inconsistent, and detached parenting behaviors were related to CD symptoms; and family environment characterized by low cohesion, high conflict, and low marital satisfaction was related to CD and depression symptoms. For the teacher-defined ADHD group, parenting variables also predicted depression symptoms. Academic and cognitive variables did not predict CD or depression symptoms when parenting, family, and peer relationship variables were taken into account. Depression prospectively predicted CD, but not the reverse, and parental hostile control and familial conflict prospectively predicted CD for the teacher-defined ADHD group only. Conclusions: Source-specificity is a useful consideration when describing the relation of parenting and home environment with CD and depression symptoms in boys with ADHD. Intervention efforts that address these parenting, family, and peer relationship variables may aid in preventing the development of comorbid conditions.