Catalytic fluorination of HCFC-133a was performed over various forms unsupported and supported chromium oxides. Catalytic activity is strongly dependent on the morphological structure of chromia. Increased conversion is observed as the crystallinity of chromia decreases. The best catalytic activity and strongest resistance against deactivation observed with CrOx/MgO is attributed to the presence of highly dispersed chromium species (isolated Cr(VI) and oligomeric Cr-Q-Cr species) on the support surface.