We compared disruptive behaviors in boys with either autism spectrum disorder (ASD) plus ADHD (n = 74), chronic multiple tic disorder plus ADHD (n = 47), ADHD Only (n = 59), or ASD Only (n = 107). Children were evaluated with parent and teacher versions of the Child Symptom Inventory-4 including parent- (n = 168) and teacher-rated (n = 173) community controls. Parents rated children in the three ADHD groups comparably for each symptom of oppositional defiant disorder (ODD) and conduct disorder. Teacher ratings indicated that the ASD + ADHD group evidenced a unique pattern of ODD symptom severity, differentiating them from the other ADHD groups, and from the ASD Only group. The clinical features of ASD appear to influence co-morbid, DSM-IV-defined ODD, with implications for nosology.