The nano-structural properties of non-stehiometric hydrogenated amorphous silicon carbide thin films, deposited by magnetron sputtering in wide range of carbon concentration (5-50 at.%) and high hydrogen content (17-45 at.%), were analysed by GISAXS (Grazing Incidence Small Angle X-ray Scattering). The film composition and density were estimated by combining vibrational spectroscopy, RBS (Rutherford Backscattering Spectrometry) and ERDA (Elastic Recoil Detection Analysis). It was found that by increasing carbon and hydrogen concentration, the film density decreases, indicating the increase of voids contribution. The GISAXS was performed on ELETTRA synchrotron radiation source, Trieste (Italy). The obtained results show the presence of 'particles' with variation in mean dimensions between 1.7 and 2.5 nm and broad size distribution. The size of 'particles', most probably large voids or voids agglomerates, increases with carbon to silicon ratio and decreases with hydrogen concentration. (C) 2003 Elsevier Science B.V. All rights reserved.