Examined whether attention-deficit/hyperactivity disorder (ADHD) and callous-unemotional (CU) traits moderate the association between conduct problems (CPs) and impairment and aggression. Participants were 214 children who were rated by their elementary school classroom teachers. Results indicated that the association between CP and impairment and aggressive outcomes is almost always moderated by ADHD and/or CU. Moreover, in many instances, the association between CP and outcomes was moderated by both ADHD and CU such that the moderating effects of CU on CP were more pronounced at lower levels of ADHD. Results are discussed with respect to developmental taxonomies and trajectories of the disruptive behavior disorders. Aggr. Behav. 34:139–153, 2008. © 2007 Wiley-Liss, Inc.