Irradiation of dihydropyridone 1a in water yields mainly the unsaturated amides 3 (73%), 4 (8%), and acetone. A 1.3% yield of photohydration product 5a is also obtained. Irradiation of 1a in anhydrous methanol yields carbinolamidoether 8 (57%), whereas in t-butyl alcohol enamide 7 is the reaction product. Irradiation of the N-methyl derivative of 1a (1b) yields 90% of starting material and 5% of a photohydrate 5b. The mechanistic path of the reaction is shown to involve the cleavage of compound 1a to the enolic form 9 of the acylimine 6 which reacts differently depending on the solvent used.