To examine the convergence of categorical and empirical diagnostic systems to evaluate whether psychiatric comorbidity of juvenile major depression with attention-deficit hyperactivity disorder (ADHD) is due to assessment bias. Using total predictive value and the odds ratio, the authors evaluated the convergence of Child Behavior Checklist (CBCL) scales with structured interview-derived diagnoses in 94 children with major depression, 97 with ADHD, and 115 normal control children with neither diagnosis. The CBCL Anxious/Depressed scale discriminated depressed from nondepressed children irrespective of comorbidity with ADHD, and the Attention Problems scale discriminated ADHD from non-ADHD children irrespective of comorbidity with major depression. Children with major depression comorbid with ADHD had CBCL correlates of both syndromes. Since the CBCL is an empirically derived taxonomic system, the correspondence between the content-congruent CBCL scales and DSM-III-R categorical diagnoses of major depression and of ADHD indicates that previously reported findings of high overlap between these two disorders using structured diagnostic interview methodology and trained raters were not due to rater biases.