Although attention-deficit/hyperactivity disorder (ADHD) is independently associated with both anxiety and conduct problems, it is unclear how co-occurring ADHD + anxiety are associated with different forms of conduct problems. That is, there is relatively little evidence how ADHD and co-occurring anxiety, relative to ADHD only and anxiety only, are associated with aggression and delinquency. Controlling for age, sex, oppositional defiant disorder diagnostic status and total psychopathology, we compared children with anxiety only, ADHD only, ADHD + anxiety, and a clinic-referred comparison group on measures of conduct problems. Three hundred eighty ethnically diverse boys and girls ages 5 to 17 (M = 11.62) were evaluated using a semistructured diagnostic interview for ADHD and anxiety; aggressive and delinquent behavior were evaluated using the Child Behavior Checklist. Children with anxiety only (n = 119) did not differ from clinic-referred comparisons (i.e., no DSM-IV diagnosis; n = 95) on aggression or delinquency; children with ADHD only (n = 130) were significantly more aggressive and delinquent than children with anxiety only. Children with ADHD + anxiety (n = 36) were significantly less aggressive than children with ADHD only, but they did not differ with respect to delinquency. These preliminary data suggest that ADHD, in the presence of anxiety, may be associated with significantly less aggression but not less delinquency. We discuss these findings from a developmental psychopathology framework and stress the need for further study to support possible implications for intervention and prevention.