Nowadays, the processes aimed at the deep conversion of heavy oil are of great interest. Polyaromatic and sulfur-containing compounds (such as anthracene and dibenzothiophene) are one of the main components of heavy oil fractions which are hard to process. Catalytic hydrotreatment of heavy petroleum fractions (vacuum gas oil, light gas oil, etc.) is widely used to improve the quality of the resulting products. As the hydrotreatment of oil fractions often requires the use of harsh process conditions and consumes a high amount of molecular hydrogen, the researchers’ interest is focused on the development of novel approaches including the use of supercritical fluids. In this work, the influence of solvent in the supercritical state on the conversion and product composition of cracking and desulfurization of polyaromatic and sulfur-containing compounds is described. The experimental results showed that the use of a supercritical solvent mixture composed of n-hexane and methanol allows the polyaromatic compounds to be effectively converted into monoaromatics providing a high conversion degree (up to 95 %).