Purpose: Investigate the quality of mothers’ interactions with children with ADHD and a marginal disturbance in socioemotional competence (MDSC). Research Methods: A total of 49 mother-boy dyads were included, and we observed their communication on neutral and conflict topics for children with ADHD and MDSC, children with ADHD alone, and children with typical development (TD). The Chinese version of the Specific Affect Coding System 20-code was used to examine the affective presentation in communication. Results: Mothers of children with ADHD and MDSC had less negative disengagement affect compared with those of children with ADHD alone. Boys with ADHD and MDSC and boys with TD had constant positive engagement between neutral and conflict conditions in parent-child interaction. Boys with ADHD and MDSC had significantly less positive affect and more neutral affect than children with ADHD only. Conclusions and Implications: Boys with ADHD and MDSC and their mothers had worse quality of observed mother-child communication than children with ADHD only and their mothers.