This article proposes a methodology based on geographical information systems and factor-analysis to carry out taxonomies for mountain areas in the Catalan Pyrenees. Initially, socio-economic and spatial variables have been used in the classification of the areas. Subsequently, the discrimination of homogeneous areas becomes important in order to undertake posterior studies about their development and to facilitate the creation of specific public policies adjusted to their main competitive advantages. The confrontation of such extreme and rival neighbouring uses in small Pyrenean regions -such as natural parks and productive activities- with externalities arising and affecting each others’ activities, requires governmental instruments to intervene in order to achieve a more efficient allocation of resources in the face of externalities, to decrease production where there is external cost and to increase it where there are external benefits. Necessarily, these policies would have to be related to urban planning and to take into account economic and social aspects. Keywords: local development, GIS, multivariate analysis, rural mountainous areas, natural protected areas.