Mothers and fathers often disagree in their ratings of child behavior as evidenced clinically and supported by a substantial literature examining parental agreement on broadband rating scales. The present study examined mother-father agreement on DSM-based, ADHD symptom-specific ratings, as compared to agreement on broadband ratings of externalizing behavior. Using mother and father ratings from 324 children who participated in the Multimodal Treatment Study of Children with ADHD, parental agreement was computed and patterns of disagreement were examined. Mother-father ratings were significantly correlated. However, a clear pattern of higher ratings by mothers compared to fathers was present across ratings. Agreement on ADHD symptom-specific ratings was significantly lower than agreement for broadband externalizing behaviors or ODD symptoms. Of several moderator variables tested, parental stress was the only variable that predicted the discrepancy in ratings. Disagreement between parents is clinically significant and may pose complications to the diagnostic process.