The present invention concerns a method of producing at least one compound of formula (II): CF3—CX(Z)n—CHX(Z)n in which X represents, independently, a hydrogen, fluorine or chlorine atom, Z represents, independently, a hydrogen or fluorine atom, and n =0 or 1, from at least one compound of formula (I): CX(Y)2—CX(Y)m—CHmXY in which X and Y represent, independently, a hydrogen, fluorine or chlorine atom and m =0 or 1. The method comprises at least one step during which at least one compound of formula (I) reacts with HF in the gaseous phase in the presence of a fluorination catalyst in order to give at least one compound of formula (II), characterised in that the catalyst is made from chromium oxyfluoride containing at least nickel as the co-metal and at least one rare earth metal.