The complex of physicochemical methods of analysis (elemental analysis, cryoscopy in benzene, IR and H-1 NMR spectroscopies, structural group analysis, gas chromatography-mass spectrometry, and selective chemical cleavage of sulfide and ether bonds) is used to comparatively characterize resins and asphaltenes of light and heavy oils. Attention is paid to the study of their structural group composition and the composition of moieties bound in molecules of resin-asphaltene substances (RAS) through ether and sulfide bridges, as well as the composition of compounds occluded by asphaltene molecules and nitrogen bases of resins. It is found that resins and asphaltenes of the heavy oil are characterized by higher average molecular masses and large overall sizes of mean molecules, due to the increased content of aromatic cycles in the naphthenic-aromatic system. The similar sets of linear and branched alkanes, alkylcyclopentanes, alkylcyclohexanes, steranes, mono- and disubstituted alkylbenzenes, and dibenzothiophenes identified in occluded compounds and products of chemolysis of resins and asphaltenes under study suggest the presence of most of these compounds as structural fragments in RAS molecules of light and heavy crude oils under study. Alkyl-substituted quinolines and benzoquinolines are identified in the nitrogen bases of resins. The feature of the light oil is the presence of "sulfur-bound" alkenes and polycycloalkenes in the structure of its asphaltenes. The findings expand our understanding of the structure of petroleum resins and asphaltenes. They can be used to simulate their structure in developing new controlled methods for processing hydrocarbon feedstock.