Direct irradiation of o-cinnamylphenols 1a-c led to mixtures of the cis-isomers 3a-c, the dihydrobenzofurans 4a-c and the dihydrobenzopyrans 5a-c. Under the same conditions, o-hydroxystilbenes2a,b gave their cis-isomers 9a,b as single photoproducts. Using 2,4,6-triphenylpyrylium tetrafluoroborate as photosensitizer the reactions of the methyl- or methoxy- substituted derivatives appear to proceed via single electron transfer. Compounds 1b,c underwent oxidative fragmentation to the aldehydes 8b,c while 2b cyclized to benzofuran 10b.