The effect of the structure of Alf(3) supports in CrF3/AlF3 catalysts and their activity were studied, and a selection of suitable reaction conditions for fluorination of trichloroethylene and HCFC-133a was made. We found that neither AlF3(alpha- and gamma-modifications) nor CrF3/alpha-AlF3 exhibits significant activity for the reaction of HF with CCl2=CHCl or CF3CH2Cl. However, CrF3/gamma-AlF3 exhibits high activity, which increases with increasing surface area and decreasing crystallite size of the gamma-AlF3 support, and that dramatically affects the fluorination of CF3CH2Cl. Investigation of a series of CrF3/gamma-AlF3 catalysts shows that the turnover rates per unit of the total surface area and of the free CrF3 surface area significantly increase with increasing content of Cr3+ loading. Optimum temperature for the reaction of HF with CCl2=CHCl is 260 degrees C, while with CF3CH2Cl it is 350 degrees C, with flow ratios HF:TCE=6:1 and HF:HCFC-133a=10:1.