The authors' goal was to assess neuropsychological performance in girls with attention-deficit/hyperactivity disorder (ADHD) and evaluate the role of comorbid learning disabilities (LDs). Participants were 140 girls with ADHD and 122 girls without ADHD, ages 6-17 years. Neuropsychological performance was measured in a standardized manner, blind to clinical status. LD was defined by a combined regression-based and low-achievement classification. ADHD was associated with modest, but significant, neuropsychological impairment, as measured with an aggregate measure of performance and with the Stroop Color-Word Test, independent of age, social class, IQ, and psychiatric comorbidity. Neuropsychological deficits were most pronounced in girls with both ADHD and an LD and in those without medications. These results extend to females the previously documented association of LDs with neuropsychological functioning in males with ADHD.