A decision support system for forest biomass exploitation for energy supply is presented. The system allows supporting decisions on a finite time horizon, concerning the localization, sizing, and setting of a number of biomass-to-energy conversion plants in a small-medium region. The system is based on the formalization of an optimal decision problem stated with reference to a dynamic biomass model. In the proposed approach, geographic information system based techniques are integrated with mathematical programming methods yielding a comprehensive system which allows formalizing the problem, taking decisions, and evaluating their effects. The application to a real case study is considered. Keywords: Decision support systems, Renewable energy systems, Planning, Energy distribution, Information systems.