Irradiation of 3-hydroxy-2,2-dimethyl-l-(0-methylary1)-alkan-1 -ones 1 a-h having a bulky alkyl group or an aryl group on C-3 in methanol gave trans-and cis-cyclopropane-1.2-diols 2a-g and 3a. c-f, h and benzocyclobutenols 4a-h through pand y-hydrogen abstractions. Irradiation of 3hydroxy-2.2dimethyl-I -(o-methylpheny1)-alkan-1 -ones 1 i-k having ethyl, methyl or no substituent at C-3 gave benzocyclobutenols 4i-k and 1,3-diketones 5i, j, but no cyclopropane-l,2-diols. The cyclopropane-1,2-diols were sensitive to air and readily oxidized to the corresponding 1,3-diketones. Irradiation of 3hydroxy-4,4-dimethyl-I -(0-methylary1)pentan-I -ones 8a, b having a methyl group or no substituent on C-2 gave benzocyclobutenols 9a, b, the peroxide 10 and phthalides 11 a, b. 3-Hydroxy-2,2-dimethyl-1,3-diphenylpropan-l -one 12a and 3hydroxy-2,2,4-trimethylpentan-l -one 12b also underwent photocyclization through phydrogen abstraction to give cyclopropane-I ,2-diols 13a. b and 14.