Child-friendliness is a concept much related to policy practices. We as researchers try to inform policy makers (and designers and politicians as well) about the child-friendly (or: child-unfriendly) character of residential environments with the ultimate aim to claim improvements. How can we outline our research in a way that meets this aim? Over the last years I carried out several studies about children’s spending of time and using of space in different urban neighbourhoods. Broadly speaking these studies can be distinguished in three categories: observation studies in playgrounds/neighbourhoods, surveys / interviews with children, surveys/interviews with parents and other adults involved with children. Each of these research-approaches has their specific strength and weakness in the sense that they offer us quite different results, while the impact of the outcomes differs accordingly. In this paper I will reflect on some of these studies and the value they have (had) for spatial design and urban planning. I will pay attention to the difficult relationship between observation and interpretation, the different positions of children and between children and parents, and the complex relationship between behaviour and environment. In addition, I will go into the question of the environment as ‘a matter of fact’ for children when referring to their daily live in the neighbourhood. In the discussion, I will argue that the discipline of urban design can best be informed with observation studies (added with interviews), while departments of urban planning can benefit more from notions derived from interviewing/survey studies.