One of the more challenging aspects of sustainability policies is to address social justice. Often, so-called sustainability initiatives turn out to be completely out of touch with the needs and expectations of the populations concerned, and contribute to increase social injustice. This is particularly true in urban areas, which are the ambit of this chapter. How to cope with this problem? Promoting people's place-based appropriation of sustainability policies looks like an interesting lead to follow. The challenge here is to address the social process of decisionmaking. Ultimately, the challenge is design a new social contract: matter in which a comprehensive understanding of the coordination mechanisms between the local, national, regional and international scale is crucial. Keywords Transition to sustainability • Social process of decision-making • Urban planning • Multilevel governance • Imported sustainability Achieving a livable and sustainable future in a changing world is a crucial challenge that our societies are facing. On this point, everybody agrees. Though, when it comes to determining how to do this practically, or simply what sustainability really is about, and, there is much less consensus. Addressing the antagonisms between social justice and sustainability is a way amongst many to address transition to sustainability. This chapter focuses on the sharp processes of spatial differentiation and the many-fold confl icts between urban sustainability and social justice. The reason why it is so diffi cult to answer the basic question of what sustainability is lays into the fact that sustainable development is not only about science. It also is about ideas and values (Leiserowitz et al. 2006