With the aim of obtaining a porphyrin derivative useful for diagnosis and therapy of cancer, fluorine analogues of protoporphyrin, in which the vinyl group(s) were replaced by difluorovinyl group(s), were synthesized by the reaction of the formylporphyrins with sodium chlorodifluoroacetate in the presence of triphenylphosphine. Some improvements in the reported procedures for the synthesis of formylporphyrins are also described. Preliminary results of biological tests of the products showed that 8², 8²-difluoroprotoporphyrin accumulates to gastric cancer more selectively than other fluorine analogues and that 3², 3², 8², 8²-tetrafluoroprotoporphyrin is taken up by rat hepatoma cells more readily than the others.