[en] Monoenergetic neutron sources in the intermediate energy range are scarce and the development of neutron therapy techniques depends on the design of neutron beam producing facilities. The paper deals with a theoretical and computational demonstration of the possibility to select quasi-monoenergetic intermediate neutrons from broad energy spectra by elastic scattering. Although heavy materials scatter nearly isotropically intermediate neutrons, on special geometrical conditions as thin blades, it is possible to get anisotropic response for neutrons of a certain energy and to select them from a broad energy spectrum. Materials useful for such selectors are those presenting at least one dominant elastic scattering cross-section peak in the intermediate neutron energy range, like iron and nickel. A verification of the theoretical demonstration has been performed by numerical simulation using the MCNP-4A code. Computation results for selecting devices made of iron and nickel show that a quasi-monoenergetic neutron field of 28.2 keV can be obtained from iron and respectively 15.6 keV from nickel. Due to the small efficiency of the scattering process, the use of a focusing device is necessary to significantly enhance neutron selection efficiency. The design of such a focusing device is proposed in the paper. (author)