Over the last three decades the environmental, economic and social crisis and the challenges and possibilities offered by new technologies have become the drivers of plans and projects for sustainable cities. In the face of a wide experimentation, the aim of this paper is to answer the question: what progress is implemented by the goal of sustainable city? To this end, I hold it is important point at the watershed between the declared intended goals of the projects realized to date and the results on the ground. To analyze this discrepancy, I have identified a common theory-practice gap in the form of the three pitfalls of sustainable city, which bring about economic and ethical conflicts and risks creating socio-spatial utopias. The three pitfalls are: (1) the idea of the city as a business; (2) the oversimplification of urban complexity; (3) the quest for the ideal community. This conceptual framework has two purposes. First, it helps to systematize the existing literature on the sustainable city project, focusing on few selected issues. Second, it offers a project evaluation framework, useful both for the management of resources and for the planning of urban space. To pinpoint these pitfalls in projects for sustainable cities could allow us to adopt a holistic approach to the city project and practice.