In polycentric urban regions one can find different, mutually related cities without a clear centre. In these regions cities cooperate to attract inhabitants and employment, but at the same time they are each other’s competitors. The Randstad (Netherlands) and the Rhine-Ruhr area (Germany) both can be seen as polycentric regions. The authors explore to what extent these regions possess a common identity and common agenda and to what extent this promotes the sustainability and energy transition of these regions. In both regions identity appears to have grown especially at subregional level, by historically developed spatial-economic profiles of the different cities or suburban regions. In addition the cities in these regions more and more wish to distinguish themselves in the area of sustainability. Every city wants to be the smartest, greenest and healthiest, and to be at the forefront in energy transition and climate mitigation. In the Dutch Randstad this competitive drive especially seems to contribute to the realization of sustainability projects at the local level. And that is exactly why regional cooperation is important: to allocate resources as well as possible and to avoid transfer to others. This can be improved by the development of subregional or regional sustainability visions.