Background: We studied the symptomatology of conduct/oppositional defiant disorder and major depression/dysthymic disorder in "pure" and comorbid presentations. Method: The sample comprised 382 children of 8 to 17 years of age attending for psychiatric outpatient consultation. Ninety-two had depressive disorders without conduct disorders, 165 conduct disorder or oppositional defiant disorder without depressive disorders and 125 had both. Results: In general, there were few differences in the distributions of the symptoms of shared disorders between the pure and the comorbid groups. Comorbidity accentuated depressive and emotional symptoms and functional impairment. After controlling for the presence of other disorders and severity of symptoms, comorbid children were more globally impaired than the pure conduct group and more impaired than the pure depressive group in school, the home, and in relationships with other people. Conclusions: The clinical presentations of "pure" and comorbid depressive and conduct disorders are similar. Differences found in phenomenology and in functional impairment between the groups have implications for treatment planning and for nosology.