The review discusses currently relevant methods for studying petroleum resins. A significant proportion of the research work deals with the study of resins in heavy oils, for which experimental approaches have been systematized and the possibilities and limitations of the mass spectrometric, spectroscopic, X-ray, and chromatographic methods have been discussed. Published data on the effect of resins on the stability of asphaltenes in heavy oils and other petroleum stocks has been analyzed. In addition to experimental approaches, an important factor for understanding the role of resins in the aggregation of asphaltenes is studying their intermolecular interactions using quantum-mechanical calculations. Commonly known approaches to the concentration, fractionation, and purification of heteroatomic petroleum components from heavy oil resins using extraction and chromatographic methods for the isolation of chemical compounds from complex multicomponent mixtures have also been considered.