Definitions of environmental child friendliness offer broad criteria that are not easy to study or assess. We suggest that due to this broadness, these definitions have produced surprisingly few attempts to evaluate how child-friendly various types of physical environments are. The purpose of this study is to analyse how the structure of the built environment contributes to environmental child friendliness. We define child friendliness by two central criteria: children’s possibilities for independent mobility and their opportunities to actualize environmental affordances. We study how built environment qualities condition environmental child friendliness in place-based ways by asking children and youth in Turku, Finland, to tell about their meaningful places and their mobility to these. The data consists of over 12,000 affordances, localized by the respondents. This experiential and behavioural place-based knowledge is combined with objectively measured data on residential and building density, and quantity of green structures. Moderate urban density seems to have child-friendly characteristics such as an ability to promote independent access to meaningful places and the diversity of affordances. We find that affordances situated on residential areas are likely to be reached alone, whereas access to affordances situated in densely built urban cores is less independent. The proportion of green structures is not associated with independent access. The diversity of affordances is highest in areas that are densely populated and not very green. Green areas are important settings for doing things, and green structures around emotional affordances increase the likelihood of liking the place significantly. Combining children’s place-based experiences with information derived from objective measurable qualities of the physical environment provides a valuable methodological contribution to studies on environmental child friendliness, and the two proposed criteria of child friendliness are supported by this study. There is no one environment that is child-friendly, but different environments have different uses and meanings.
