Abstract: This paper reports on a case study on community formation and attitudes to sustainability in three Canberra suburbs, building on literature that see a strong sense of community as a necessarily element of making cities more sustainable. The paper compares attitudes in Greenfield sites to those in urban infill developments, Brownfield sites. The Greenfield study site is further sub-divided into low and higher-density developments. Through a range of interviewees and focus groups across a diversity of socio-economic backgrounds, actual attitudes to community and to sustainability are elicited. The study uses a twin comparative method, first comparing and contrasting the low- and medium-density Greenfield sites, and then comparing and contrasting the Greenfield sites with the Brownfield site, with a particular focus on how urban infill developments are perceived as affecting pre-existing community networks. Implications are drawn for urban planners and policy makers, especially in relation to how they might design to both create, or strengthen, community and how this might in turn foster positive community attitudes to sustainability.