The long lasting interest in diluted magnetic semiconductors (DMS) relies on the combination of fundamental science and the potential for spintronics applications. Despite the large body of experimental and theoretical studies carried out in the past decades, there are ongoing controversies about high-T_C ferromagnetic DMS. This paper summarizes the results of the few investigations performed by inelastic neutron scattering, which provides key information for some of the open questions. Emphasis is led on a complete study of the compound Mn_xGa_1-xN, as well as on novel DMS materials for which the spin injection is decoupled from carrier doping.