In 2009, Siemens (Germany) sponsored the research by the Economist Intelligence Unit (London), which resulted in the publication of the European Green City Index report, in which the environmental performance of 30 large cities in Europe was analysed. It provided city administrations with an idea of where they stood vis-a-vis their European counterparts. However, while adopting such performance evaluation methodologies, it is important to set targets and goals, and to be aware of pitfalls that may exist in the course of a blind pursuit of a higher Green Score. City administrations are usually segmented into different divisions and departments; often each division strives towards its own set of targets and goals, without being aware (or without being concerned, even if it is aware) of the overlaps, conflicts and synergies that may exist with the targets and goals of the others. The Green City Index needs to be considered together with an Urban Socio-Economic Index, which can be suitably structured with the inter-linkages with the indicators of the Green City Index explicitly described.