Background: Some mothers of children with attention-deficit/hyperactivity disorder (ADHD) present with maladaptive personality profiles (high neuroticism, low conscientiousness). The moderating effect of maternal personality traits on treatment outcomes for childhood ADHD has not been examined. We evaluate whether maternal neuroticism and conscientiousness moderated response in the Multimodal Treatment Study of Children with ADHD. This is one of the first study of this type. Methods: In a randomized controlled trial (RCT), 579 children ages 7-10 (M=8.5); 19.7% female; 60.8% White with combined-type ADHD were randomly assigned to systematic medication management (MedMgt) alone, comprehensive multicomponent behavioral treatment (Beh), their combination (Comb), or community comparison treatment-as-usual (CC). Latent Class Analysis and Linear Mixed Effects Models included 437 children whose biological mothers completed the NEO Five-Factor Inventory at baseline. Results: A 3-class solution demonstrated best fit for the NEO: MN&MC=moderate neuroticism and conscientiousness (n=284); HN&LC=high neuroticism, low conscientiousness (n=83); LN&HC=low neuroticism, high conscientiousness (n=70). Per parent-reported symptoms: children of mothers with HN&LC, but not LN&HC, had a significantly better response to Beh than to CC; Children of mothers with MN&MC and LN&HC, but not HN&LC, responded better to Comb&MedMgt than to Beh&CC. Per teacher-reported symptoms, children of mothers with HN&LC, but not LN&HC, responded significantly better to Comb than to MedMgt. Conclusions: Children of mothers with high neuroticism and low conscientiousness benefited more from behavioral treatments (Beh vs. CC; Comb vs. MedMgt) than other children. Evaluation of maternal personality may aid treatment selection for children with ADHD, though additional research on this topic is needed.