The effect of initial concentration of tetrachloromethane and trichloromethane on their conversion in gliding discharge was determined. The conversion of CCl4 and CHCl3 was carried out in air containing 20 or 8000 ppm of water vapor. The flow rate of the air containing 1.2, 2.5, or 6.0 vol% of CCl4 or CHCl3 was 200 Nl/h. The amount of tetrachloromethane and trichloromethane reacted was determined for a constant value of specific energy which was varied with 2.0 and 4.0 VAh/Nl. The amounts of CCl4 and CHCl3 reacted were a linear function of the initial concentration of these compounds in the inlet gas. The results obtained have shown that water vapor present in the air has a favorable effect on the conversion of tetrachloromethane and trichloromethane in gliding discharge.