•Contact with nature positively contributes to the health of people.•For the design of healthy cities, empirically substantiated metrics are required.•Type of nature, size, distance and quality are discussed.•Cumulative opportunities-based indicators of urban green space seem preferable.•For future research, more functionally oriented accessibility indicators are needed. There is growing scientific recognition that contact with nature in general, and contact with urban green more specific, have the potential to positively contribute to human health. For the purpose of developing healthy urban neighbourhoods, this raises the question how to take scientific evidence about these health benefits into account. Accessibility metrics that are well substantiated by empirical evidence are needed. This paper reviews the quantitative and qualitative aspects relevant for accessibility metrics and empirical studies addressing these aspects in relation to health. Studies comparing different types of green space indicators suggest that cumulative opportunities indicators are more consistently positively related to health than residential proximity ones. In contrast to residential proximity indicators, cumulative opportunities indicators take all the green space within a certain distance into account. Comparing results across studies proved to be hard. Green space accessibility was measured in a variety of ways and the green space indicator that was chosen was often not problematized. We feel that it is time for a more function-oriented approach. How precisely does contact with nature impact health and what type and qualities are relevant in this regard? We think this will lead to a new generation of more evidence-based accessibility metrics that will help to advance the field.