The Centre-Val de Loire is a French Region, where green spaces have a long history, linked to its castles: it was considered as the garden of France. In the framework of a research program, we chose this Region to study the cultural ecosystem services offered by urban green spaces (UGS). We focused on the six medium cities of the Region to conduct an interdisciplinary study. Our goal was to make municipalities aware of the importance of their UGS, in a context of budgetary restriction. But between the theory (described by the Millenium Ecosystem Assessment for example) and the practice, several difficulties appear. The first one concerns the interdisciplinary researches; we decided to go beyond this problem by focusing on the same UGS. The second difficulty is about assessment. Different methods are used, especially economic ones or based on models. But our purpose was to identify what UGS provide with city dwellers and the assessment also implies some choices, which can be questioned: criteria, reference, generalization possibilities. Finally, a qualitative study appears more interesting: it reveals more information about the services offered by the different UGS categories and leaves the possibility of considering also disservices, which are often forgotten. One of the relevant results concerns the allotment gardens: they appear to be places of sociability and education, providing services not only for the gardeners. Beyond these gardens, UGS prove complementary. Each one has a function, according to users but also time, especially between weekdays and weekend, and it even concerns the less busy gardens. Organizing each UGS into a hierarchy is difficult, even if we consider the quantitative studies, based on ecological or soil criteria and even economic data (they are not enough). But this hierarchy is finally not necessarily: more than a specific UGS, it is the global supply of UGS, which makes a city more eco-civilized.