The homopolymer of 2-(4-ethenyl)phenyl-5-phenyl-2H-tetrazole and its copolymers with styrene and acrylonitrile were prepared and characterized by thermoanalytic and spectroscopic methods. Photochemically induced crosslinking and modification of these polymers with vinylic agents such as acrylic acid, methacrylic acid and its derivatives through 1,3-dipolar cycloaddition was investigated in solution and thin solid films. It was proved by UV- and ATR/FTIR-spectroscopy that the reaction of the polymers with the modifiers leads to the formation of heterocyclic structures.