Since two decades or so urban development in megacities around the world is increasingly put forward through publicprivate, large scale modernization and investment projects. Examples are super-modern highways and toll roads, industrial enclaves and entire new towns (master-planned communities) on the outskirts of cities. Especially the dimensions and design characteristics of the latter have been described in case studies for Asia and Latin America. Due to the parallel emergence of the phenomenon in many large cities around the world, the global similarities in terms of concept and design (following mostly US-examples) and the involvement of international financial capital, projects are often labelled as a product of globalization. Furthermore, the often involved transfer of planning power from public to private actors and the privatisation of beforehand public space is seen as an expression of neoliberal urban governance and the neoliberalization of urban space respectively. While it might hold true that neoliberal globalization is a structural root cause of new forms of urban development on a general level in cit- ies around the world, more is needed to understand and explain the emergence and implementation of projects in concrete and particular places and the consequences for particular groups of people, especially the most vulnerable ones. Furthermore, from a sustainability perspective it seems especially relevant to ask which role the state and civil society - potential defenders of some form of public interest – actually play (and might play in the future) in planning processes which are shaped by powerful private interests. Detailed case studies are needed that look at the complex interplay of different groups of actors, their interests, strategies as well as the outcomes of decision-making. Taking political ecology as a general research framework and sociological institutionalist/ relational governance analysis as a methodological device, in this paper I will try to shed some light on these issues using Santiago de Chile as case study. Here large scale greenfield development projects are realized and planned in a number unprecedented in Latin America. Projects on superficies altogether bigger than 9000 hectares and an investment volume higher than 10 billion dollars have been constructed since 2002 or are in their final planning stage. In my PhD-project I focus on the two communities of most intense project development in the last years, Colina and Pudahuel, and here the story of two emblematic master-planned communities, Piedra Roja and Urbanya. Through qualitative methods as semi-structured interviews and document analysis I study the logics and rationalities that explain the actions of the involved actors and the power configurations at play leading to concrete outcomes of planning and negotiation processes. I am especially interested in the strategies of public authorities and civil society to get a grip on privately led development. Actually, the projects are based on the introduction of planning obligations into land-use planning (in Chile the respective instruments are called ‘Conditional Development Zones, ZODUC’, and ‘Conditional Development Projects, PDUC’), profoundly affecting the way urban development is and will be negotiated in the future. While the first generation of projects negotiated under the new scheme (Colina) ended up as elite enclaves hardly considering public interest in any form, the second generation of projects (Pudahuel) is socially and environmentally more sound and does consider local communities and some sustainability criteria which can be explained through strong local leadership and community mobilisation in Pudahuel. This highlights that large projects are at the same time expression and driver of more generalized changes in the realm of planning principles and procedures on the local, regional and even national scale with important impacts on people and their environments.