The whole totality of the light aromatic hydrocarbons has been investigated in composition of the naftalan oil. As a result of investigations has been exporsured a number of aromatic, naphthenic and aromato-naphthenic rings. The percent content of the carbon atoms in rings and in side chains has been determined. At study of vacuum and thermo-diffusion fraction of light aromatic hydrocarbons there has been determined content of alkyl benzol, indan, tetralin and dynaphthen benzol.