Photochemical reaction of a zinc chlorophyll-d derivative possessing a formyl group at the 3-position with a reductant in a deaerated alcoholic solution gave the corresponding 3-unsubstituted chlorin in 43% yield based on consumed starting material. The novel deformylation was accompanied by expected 2,3- or 7,8-dihydrogenation to give minor products possessing a isobacteriochlorin or bacteriochlorin pi-system, respectively, as stereochemical mixtures.