An investigation has been made of certain relationships governing the photo-oxidation of catalytic cracking gas oil fractions (CCGOF). The role of aromatic hydrocarbons in the formation of singlet oxygen (O-1(2)) and the participation of the latter at the initial stages of the photochemical process have been established. The values of the parameter characterizing the reactivity of hydrocarbons in CCGOF in relation to O-1(2) have been determined. Inhibitors of the photo-oxidation of CCGOF have been established, and their stabilizing effect has been assessed.