The rate of photochemical reaction in solutions of luminescent platinum(II) complex with 8-quinolinol was studied in relation to the type of solvent, irradiation time, photon energy and intensity of a luminous flux, concentration of the complex, and presence of oxygen. The structure of the photochemical reaction product was studied by X-ray photoelectron, IR, and electronic absorption spectroscopy. The quantitative kinetic parameters and quantum yield of the photochemical reaction performed under various irradiation conditions are reported.