The primary sector has always had a fundamental role in human activities. In recent years, major industrialised and developed countries increased demand for the positive externalities generated by the agriculture, while they reduced the importance of the sector in terms of production of food. The evolution of public intervention followed the change of the role of agriculture and has tried to propose instruments able to consider and balance both private and public interests. It is especially with the Mid Term Review (MTR) that policy maker has tried to implement a system of subsidies that bound the farmer to a series of activities related either directly or indirectly with the collective welfare. Moving from coupled aid to decoupled one linked to the respect of cross-compliance means changing the concept of public intervention. In this context, a useful evaluation tool should be able to analyse and to catch the changes in farmers behaviour by considering also the territory in order to locate the effects. The territory, as a matter of fact, is not only the place where the effects passively fall, but it is capable of interfering directly in the farmers decision-making process. Therefore, the development of specific methodologies able to analyze farmers’ behaviours and specific instruments linked to the territorial analysis could represent an important tool to assess agricultural policies effects both on enterprises and territory. In this framework a methodology based on the Positive Mathematical Programming (PMP) and on the implementation of a Geographic Information System (GIS) seems to answer the several questions about the policies’ assessment and land-use planning. The present research integrates this two methodologies. PMP is used in a territorial model and it is based on the optimization of an objective function representing a farm gross margin while GIS allows to analyze territorial aspects and to locate the effects of the policy. This tool has been tested in a specific case study in order to analyse the effects of the CAP Reform (in particular decoupling, cross-compliance and modulation) on the primary sector and on farm land use potential changes. The innovative aspect of the research is the attempt to study the impact of agricultural policy through an optimization model that considers among its variables also the specific localization of farms. The final result is represented by the creation of georeferred maps in which the land use changes are evaluated and interpreted under the framework of multifunctionality, in terms of quantitative analysis regarding landscape and, abandonment risk and cattle distribution.