The behavior of paramagnetic defects and dark conductivity in heterogeneous samples of hydrogenated nanocrystalline carbon-containing silicon (nc-SiC:H) prepared by the photo-CVD method is studied. It is shown that, with increasing carbon content in nc-SiC:H, a phase transition from a nanocrystalline to an amorphous structure occurs, producing a reduction in paramagnetic defect density and a significant decrease in the dark conductivity. (C) 2004 MAIK "Nauka/Interperiodica".