This article intends to analyse this transition process towards a post-carbon model in 10 European cities (Barcelona, Copenhagen, Malmö, Istanbul, Lisbon, Litoměřice, Milan, Turin, Rostock and Zagreb) based on a set of environmental, economic and social Key Performance Indicators (KPI). This research work identifies a global trend towards a post-carbon paradigm, besides different urban development stages. Copenhagen and Malmö are at the forefront of this sustainable trajectory. These cities have clear strategic visions in the area of urban sustainability, and are implementing several projects on mobility, energy and climate with positive impacts. Moreover, they are young, qualified and multicultural cities and present a good economic performance in terms of GDP per capita, which emphasises the importance of good framework conditions.