Background: Boron Neutron Capture Therapy (BNCT) is a very promising treatment for patients suffering gliobastoma multiforme, an aggressive type of brain cancer, where conventional radiation therapies fail. Thermal neutrons are suitable for the direct treatment of cancers which are located at near-tissue-surface deep-seated tumors need harder, epithermal neutron energy spectra. Materials and Methods: In this work a BNCT facility based on a compact D–D neutron generator, has been simulated using the MCNP4B Monte Carlo code. The materials considered, for the design of the facility, were chosen according to the EU Directive 2002/95/EC, hence, excluded the use of cadmium and lead. Results: An extensive set of calculations performed with MCNP4B Mote Carlo code have show that the combination of TiF3 which integrates a conic part made of D2O, then followed by a TiF3 layer is the optimum moderator design. The use of BiF3 as spectrum shifter and &gamma rays filter, Titanium as fast neutron filter and Lithium as thermal neutron filter is necessary in order to obtain an epithermal neutron beam with high quality. Conclusion: The simulations show that, even if the neutron flux is below the recommended value for clinical treatment, the proposed facility is a good alternative for clinics which cannot afford to build and maintain a small nuclear reactor.