We have deposited diamond-like carbon (DLC) films by reactive radio-frequency magnetron sputtering using hydrogen gas, and have investigated structure, chemical bonding, surface morphology and adhesion strength of the films. The film properties have been characterized by visible Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy and scratch test. It has been clarified that the fraction of sp(3) bonds in the deposited films, as estimated from C1s XPS peaks, increases with an increase in hydrogen-gas flow rate. The Raman spectra show the G and D peaks near 1580 and 1370 cm(-1) respectively, and the intensity of the D peak decreases with an increase in hydrogen-gas flow rate, which indicates disordering of the amorphous-carbon films. The influence of hydrogen on the structural and mechanical properties has been discussed.. (c) 2005 Elsevier B.V All rights reserved.