Objective: We examined whether severity scores (1 SD vs 2 SDs) of a unique profile of the Child Behavior Checklist (CBCL) consisting of the Anxiety/Depression, Aggression, and Attention (AAA) scales would help differentiate levels of deficits in children with attention-deficit hyperactivity disorder (ADHD). Study Design: Subjects were 197 children with ADHD and 224 without ADHD. We defined deficient emotional self-regulation (DESR) as an aggregate cutoff score of >180 but <210 (1 SD) on the AAA scales of the CBCL (CBCL-DESR) and Severe Dysregulation as an aggregate cutoff score of ≥210 on the same scales (CBCL-Severe Dysregulation). All subjects were assessed with structured diagnostic interviews and a range of functional measures. Results: Thirty-six percent of children with ADHD had a positive CBCL-DESR profile versus 2% of controls (p < .001) and 19% had a positive CBCL-Severe Dysregulation profile versus 0% of controls (p < .001). The subjects positive for the CBCL-Severe Dysregulation profile differed selectively from those with the CBCL-DESR profile in having higher rates of unipolar and bipolar mood disorders, oppositional defiant and conduct disorders, psychiatric hospitalization at both baseline and follow-up assessments, and a higher rate of the CBCL-Severe Dysregulation in siblings. In contrast, the CBCL-DESR was associated with higher rates of comorbid disruptive behavior, anxiety disorders, and impaired interpersonal functioning compared with other ADHD children. Conclusion: Severity scores of the AAA CBCL profiles can help distinguish 2 groups of emotional regulation problems in children with ADHD.