Territorial cohesion, at the same level than social cohesion and economic cohesion, lies at the core of the European model of society. This thesis intends to understand how far is a national spatial planning policy modified by the europeanisation process. It appears that the main issues at stake in Turkey are the huge regional disparities between the East and the West of the country, but also at a regional scale between metropolitan major cities and declining rural areas, and the lack of regional adminisrative units fostering multi-level governance. The creation of regional development agencies at regional scale in Turkey introduces new actors within the centralised development process of the country. Established at the NUTS 2 level, they a...