This paper deals with social housing urban design and related users attitudes and behaviors. The focus is on ‘traditional’ urban design, which characterized social housing design previous to modernist urbanism, and on modernist urban design. Whereas the first is characterized by a direct relationship between buildings and public open spaces, such as Karl Marx Hof in Vienna , the second is characterized by a loose relationship, with public open spaces merely resulting from the layout of blocks of flats, such as Killingworth Housing State in northeast England. In a ‘traditional’ urban design approach, buildings have front doors and windows facing the public streets, whereas in a modernist urban design approach buildings tend have doors and windows far away from the public streets and/or facing inward open spaces with no distinction between front and back windows and doors. Users’ attitudes and behaviors are discussed regarding the perception and use of public open spaces in housing estates with a ‘traditional’ urban design and in estates with modernist urban design, including perception of appearance, security and wayfinding. Although many problems have been related to the modernist urban design, a main reason for these discussions is related to the fact that the modernist urban design has been the dominant approach to social housing design, at least in the case of housing estates built in Brazil, including many of those built in the scope of the federal housing programs. Data was collected by means of questionnaires, interviews and observations carried out in housing estates with a modernist urban design and constituted by four storey blocks of flats (Rubem Berta, Sapucaia, Guajuviras, Loureiro da Silva and Angico) and in housing estates with a more ‘traditional’ urban design (IAPI – with three and four storey buildings; Princesa Isabel - four storey buildings) located in Porto Alegre and in its metropolitan region, in southern Brazil. These data was analyzed trough non-parametric statistical tests such as Kruskal-Wallis and Spearman rank correlation. The results obtained from the analyses of these housing estates are compared to those from studies about housing states such as the Killingworth Housing State and Pruitt- Igoe (St. Louis, United States). Results indicate, for example, that housing estates with a modernist urban design tend to provoke negative users’ responses concerning their appearance and use of open spaces. In the case of housing states with modernist urban design located either in Porto Alegre or in its metropolitan region, communal open spaces were illegally occupied by buildings for private use such as garages. These occupations negatively affect the appearance of housing estates, tend to make wayfinding more difficult and to increase perception of insecurity. Moreover, these findings emphasize the importance of social housing urban design in affecting users’ attitudes and behaviors and in making possible the design and provision of more sustainable social housing.