Objective: The following comorbid subgroups of ADHD have been proposed: ADHD Only, ADHD + anxiety disorders (ANX), ADHD + oppositional defiant disorder/conduct disorder (ODD/CD), and ADHD + ODD/CD + ANX. The current study examined a subset of these groups. Method: A total of 134 children and adolescents (M age = 9.92; range = 6-17) from a clinic-referred sample (n = 407) were grouped based on a semistructured diagnostic interview: ADHD only (n = 41), ADHD + ANX (n = 31), and ANX Only (n = 62). Results: Findings supported greater parent-reported anxiety symptoms in anxiety groups, and greater parent- and teacher-reported attention problems in ADHD groups. ADHD groups performed worse on a continuous performance test, whereas ADHD + ANX performed worse on working memory than ADHD Only. ADHD + ANX reported more physical anxiety symptoms than ADHD Only. Conclusion: Comorbid anxiety should be considered in ADHD assessment and treatment. (J. of Att. Dis. 2012; XX(X) 1-XX)