The invention relates to a process for preparing 2,3,3,3-tetrafluoropropene (CF3CF═CH2), performed using the steps of dehydrohalogenating 1,1,1,2,2-pentafluoropropane (CH3CF2CF3, HFC-245ca) 1,1,1,2-tetrafluoro-2-chloropropane, 1,1,1,2,3-pentafluoropropane (CH2FCHFCF3, HFC-245eb) and / or 1,1,1,2-tetrafluoro-3-chloropropane in the presence of a base, and converting a trifluorodichloropropane or a difluorotrichloropropane or a fluorotetrachloropropane to CH3CF2CF3, 1,1,1,2-tetrafluoro-2-chloropropane, CH2FCHFCF3, and / or 1,1,1,2-tetrafluoro-3-chloropropane.