Electron paramagnetic resonance and low-temperature photolysis methods have been used to study the light-induced breakdown of paraffinic hydrocarbons sensitized by a petroleum luminescent concentrate - ＇＇Shivanol＇＇. It was shown that, during the photoirradiation of frozen solutions of luminophor ＇＇Shivanol＇＇ in liquid paraffins, the intense formation of hydrocarbon radicals and H radicals is observed. Several hydrocarbon radicals were identified, the number of which changes on transition from low-molecular weight polycyclic aromatic hydrocarbons (PAH) to relatively high-molecular weight hydrocarbons. It was established that, for effective photosensitization of organic compounds, a quite definite fractional composition of the investigated luminescent concentrate with a relatively high content of low-molecular weight PAH is necessary.