Hydrogenated amorphous carbon films were obtained from the decomposition of methane using a rf-couple glow-discharged system at power densities ranging from 0.4 to 4.8 W/cm2 . The structure of as-prepared and annealed films were characterized by Raman spectroscopy, infrared absorption, photoluminescence, energy-loss spectroscopy, and x-ray diffraction. The results indicate that the incorporated hydrogen concentration is an important parameter in determining the structure and properties of the films. Carbon films deposited at a lowest rf power density contain a large amount of hydrogen with most of the C–H bonds in CH3 configurations, whereas films produced at higher rf powers reveal dominant CH2 bonding structures. According to Raman scattering measurements the sp2 domains in as-prepared samples are disordered due perhaps to bond-angle distortions. Upon annealing, hydrogen leaves the film at a temperature that depends on the initial hydrogen concentration. Once most of the hydrogen has been driven out, crystallization into the graphite phase takes place. The microcrystallite size was measured by Raman and x-ray diffraction.