The copolymer poly (VBSe-co-ST), containing photolabile selenocyanato groups, was prepared by the free-radical copolymerization of styrene (ST) with the new monomer 4-vinylbenzyl selenocyanate (VBSe). Alternatively, the copolymer poly (VBBr-co-ST), containing 4-vinylbenzyl bromide (VBBr) was treated with KSeCN to give poly (VBSe-co-ST); the copolymer poly (VBT-co-ST), containing 4-vinylbenzyl thiocyanate (VET) units, was obtained in a similar way. The photocrosslinking of these copolymers was investigated under 248 nm excimer laser irradiation. Poly (VBSe-co-ST) was found to be about four times more photosensitive than poly (VBBr-co-ST) or poly(VBT-co-ST).