The IR vibrational spectra of a-SiC:H films prepared by rf glow discharge decomposition of a mixture of silane and methane gases have been studied. The films have been prepared under different conditions which include variation of methane concentration in the gas mixture, rf power and substrate temperature. The structures of the a-SiC:H films depend very sensitively on the deposition parameters. The spectra of p-type a-SiC:H films prepared with boron doping have also been studied. The effect of annealing on the IR spectra of the films has been investigated. Attempts have been made to analyze all these data in order to obtain information about different bonded configurations in the films.