This article troubles the established discourse of free choice and free play in early childhood education, and develops post-structural approaches to theorising children's agency in the context of institutional and relational power structures. It is widely accepted that planning a curriculum based on children's needs, interests and patterns of learning promotes agency, self-regulation and control. However, contemporary research extends this discourse through critical examination of child-centred and developmental perspectives, and by theorising children's agency as a means of enacting power relationships in play. Using naturalistic, interpretive methods for documenting children's choices of play activities, this small-scale study focuses on 10 children in an Early Years Foundation Stage setting in England. Combining contemporary sociocultural and post-structural theories, the findings indicate that children's choices are situated within shifting power structures and relationships, involving conflict, negotiation, resistance and subversion. These activities create opportunities for exercising and affirming group and individual agency. The study raises critical questions about how children make and manage their choices, and examines the implications for policy and practice in light of restrictive curriculum frameworks. (author abstract)