This paper presents the results of PL and X-ray diffraction investigations for amorphous hydrogenated silicon films with and without Si nanocrystals. Hydrogenated amorphous Si layers were prepared by the hot-wire CVD method on glass substrates at the permanent mixture flow of silane /hydrogen [SiH4]/[H2] gas sources with the 7/15 flow ratio and with different oxygen flows. The joint analysis of PL and X-ray diffraction results in dependence on technological conditions and on different sizes of Si nanocrystals has been done. The correlation of optical parameters with the amorphous Si:H and crystal Si phase volumes in the films has been discussed. (C) 2009 Elsevier B.V. All rights reserved.