Oppositional defiant disorder (ODD) is associated with elevated rates of psychopathic traits and aggression. However, it remains unclear if attention-deficit/hyperactivity disorder (ADHD) symptoms exacerbate these relations, particularly in samples of children who are severely clinically distressed. The purpose of the present study was to test ADHD symptoms as a potential moderator of the relations of ODD symptoms to psychopathic traits (i.e., callous-unemotional [CU] traits, narcissism) and to aggressive subtypes (i.e., proactive, reactive aggression) in a large sample of children in an acute psychiatric inpatient facility (n = 699; ages 6–12). Multiple regression analyses indicated that, after controlling for child demographic variables, ADHD symptoms marginally exacerbated the relation between ODD symptoms and CU traits. Both ODD and ADHD symptoms had an additive, but not a multiplicative effect, in predicting narcissism. In addition, for a subset of the full sample for whom data were available (n = 351), ADHD symptoms exacerbated the relation between ODD symptoms and both reactive and proactive aggression. These results suggest that ADHD symptoms tend to have a negative effect on the relation between ODD symptoms and markers of antisociality among children receiving acute psychiatric care. Aggr. Behav. 39 :201-211, 2013. © 2013 Wiley Periodicals, Inc.