Abstract Parent and substituted flavanones undergo photochemical opening of the pyrone ring to give corresponding 2′-hydroxychalcones in benzene, pyridine, acetonitrile etc., the yields varying from 0 to 70% with substituents. The reaction is depressed by the addition of 1,3-pentadiene, nitrosobenzene, or acrylonitrile. On the other hand, flavanone and 4-chromanone undergo photoreduction in 2-propanol to give reductive coupling products and solvent adducts as isomeric mixtures. 7,8-Benzoflavanone does not undergo photoreduction in 2-propanol but the ring opening reaction instead. Mechanisms have been discussed in terms of the relative contribution and π,π* character in the lowest triplet states.