The present study explored the association between the structural quality of child care, caregivers' sensitive responsiveness, children's involvement in play and activity in the setting, and children's expression of aggression. Eighty-four early childhood care settings were classified into either high (29) or low structural quality (55) based on group size and caregivers-children ratio. Caregivers and children (14-17 months) were filmed in various episodes. Findings showed that sensitive responsiveness of caregivers in high-quality settings was significantly higher than in low-quality settings. Level of aggression in the group was lower in high-quality than in low-quality settings. We found a significant positive correlation between emotional responsiveness and involvement in high-quality but not low-quality settings. The findings demonstrate that structural quality is a necessary condition for ensuring process quality and facilitating beneficial relationships between adults and children.