Cu6PS5X (X=I, Br) solid electrolytes are obtained in nanocrystalline state by ball milling, their crystalline structure is studied and average crystallite size is estimated from X-ray diffraction. Essential low-frequency shifts of Raman scattering bands, their broadening and intensity decrease with crystallite size decrease are observed. The specific features of Raman scattering in nanometric solid electrolytes are explained within the known approaches based on the results obtained and in comparison with the bulk crystals. (c) 2008 Elsevier B.V. All rights reserved.