The gas phase hydrodechlorination of CF3CFCl2 to CF3FH2 and CF2Cl2 to CF2H2 catalyzed by Pd supported on Al2O3, a series of fluorinated Al2O3, and AlF3 was investigated. A combination of reaction kinetics investigations and characterization by in situ FTIR spectroscopy has been performed. It has been found that for reactions involving CF3CFCl2, all catalysts exhibit a rapid and significant decrease in activity; however, little change in activity with time on stream occurs with CF2Cl2. FTIR investigations suggest the occurrence of direct reaction between the CFC and the support material, which results in the consumption of hydroxyl groups during the early stages of reaction. The effect of fluorination of support on catalytic behavior of Pd is discussed.