The research reported in this paper addresses the relationship between quality of open space and health related lifestyle in urban residential areas. The research was performed in the residential developments in Ljubljana, Slovenia, dating from the time of political and economic changes in the early nineties. Compared to the older neighborhoods, these are typically single-use residential areas, with small open spaces and poor landscape design. The research is concerned with the quality of life in these areas, especially from the perspective of the vulnerable users, like the elderly and children. Both depend on easily accessible green areas in close proximity to their homes. The hypothesis is that the poor open space quality affects their health-related behavior and their perceived health status. The research has three methodological phases: (1) a comparison between urban residential areas by criteria describing their physical characteristics; (2) behavior observation and mapping and (3) a resident opinion survey. The results confirm differences between open spaces of the selected residential areas as well as their relation with outdoor activities: a lack of outdoor programs correlates with poor variety of outdoor activities, limited to transition type, less time spent outdoors and lower satisfaction with their home environment. The survey also disclosed a strong influence of a set of socio-economic variables such as education and economic status on physical activity and self-perceived health status of people. The results therefore confirm the hypothesis especially for less affluent and educated; i.e., vulnerable groups.