Mother-child interactions in 22q11.2 Deletion syndrome (22q11.2DS) and Williams syndrome (WS) were coded for maternal sensitivity/intrusiveness, child's expression of affect, levels of engagement, and dyadic reciprocity. WS children were found to express more positive emotions towards their mothers compared to 22q11.2DS children and those with developmental delay in a conflict interaction. During the same interaction, dyads of 22q11.2DS children were characterized by higher levels of maternal intrusiveness, lower levels of child's engagement and reduced reciprocity compared to dyads of typically developing children. Finally, 22q11.2DS children with the COMT Met allele showed less adaptive behaviors than children with the Val allele. Dyadic behaviors partially coincided with the distinct social phenotypes in these syndromes and are potential behavioral markers of psychopathological trajectory.