Qualitative aspects of housing environment have gained great interest in recent housing research. Research interest has shifted from environmental performance to psyche-social. and spatial quality characteristics which can be measured by users' subjective evaluations. This paper discusses quality characteristics of outdoor spaces. A model is developed to define basic dimensions of environmental quality, combining psyche-social and spatial quality characteristics. Environmental quality is thoroughly and comprehensively investigated for outdoor spaces in a research project which was conducted in Istanbul in the open spaces of three housing areas constructed with mass production techniques, having different socioeconomic and spatial characteristics.(1) Findings of visual investigations which were supported by statistical findings are presented for each mass-housing area comparatively.