The aim of this paper is to propose a new location–allocation structure, in an effort to improve the operational shortcomings of the existing locations of primary health care centers. These shortcomings are mainly caused by the preference of patients to use local hospitals rather than health centers. The method is based on a biobjective mathematical programming model for locating hospitals and primary health care centers. Two objectives are considered: (1) minimization of distance between patients and facilities, (2) equitable distribution of the facilities among citizens. We formulate the model taking into consideration the interdependence of the locations i.e. the general hospitals and health centers. This approach enables us to introduce a new aspect to the location problem, namely public preferences and also to consider the decentralization of the health care system. In order to represent the available information we employ Geographic Information Systems (GIS). We apply this model in the area of Western Greece and then compare our results with the solution originally selected by planners. Demographic data concerning the major and minor population centers of the area were based on the latest census of 2001. The results confirm the necessity of applied scientific approaches for regulating the health care system in order to establish rational strategic planning and ensure the best use of the available resources.