Oxidation rates for hydrogenated amorphous silicon carbide (a-Si1-xCx:H) films deposited from both pulsed and continuous wave (CW) SiH4/CH4 rf (13.56 MHz) plasmas have been measured using Fourier transform infrared spectroscopy. Films deposited from CW plasmas oxidize much more rapidly than those deposited from equivalently powered pulsed plasmas. The effect of a diluent gas in the feed (He, Ar, or H-2) on film oxidation rates has also been investigated With He and Ar, the CW films oxidize faster than the pulsed films. With H-2 as the diluent, however, the CW films do not oxidize as rapidly as other CW films, even after long periods of time. This is most likely the result of hydrogen radicals annealing the films through reactions with active sites on the CW films. Addition of H-2 also decreases the deposition rates in both pulsed and CW systems, suggesting H-2 contributes to the deposition reaction scheme. Additional compositional changes in the a-Si1-xCx:H materials with addition of H-2 to the plasma feed gas are also discussed.