Young children often lack opportunities to play in a physically active way. This is particularly the case for children with cancer and other chronic diseases, who regularly undergo periods of hospitalization. Promoting their physical activity and play can contribute to their health, wellbeing, and development. This thesis develops ‘Playscapes’ – a design perspective that emphasizes the unstructured and spontaneous nature of young children’s physical activity. Playscapes encourages designers to enable such physical activity through the design of open-ended and ambiguous playthings. By designing such playthings for children with cancer, this thesis contributes to turning hospital environments, such as patient rooms and waiting areas, into potential ‘landscapes for physical activity and play’.