Among 120 pairwise relations between 16 main H-1 and C-13 NMR-measurable characteristics of the structural group composition of Volga-Urals crude oils, 10 most consistent relations (correlation coefficients vertical bar r(s)vertical bar >= 0.9), 13 relations with vertical bar r(s)vertical bar in the range of 0.8-0.9, and 33 pairs with loosely related or mutually independent members (vertical bar r(s)vertical bar = 0.3) have been revealed. Several relationships are parametric. The main parameter is Car. The overall picture of the relationships is complex; correlation coefficients with the absolute value above 0.7 are observed not only between the parameters characterizing the structure in the same group of entities (aromatic, n-alkyl): it has been found that Car correlates with the total content of n-alkyl structures (r(s) = -0.76). Having definitely common features, oils from the Volga-Urals and Western Siberia oil and gas basins noticeably differ from one another. To explain the differences, it is necessary to launch an integrated study that is methodologically beyond the scope of contemporary petroleum geochemistry. The paper demonstrates the capabilities of correlation analysis for solving problems to which this method has not been yet applied in petroleum geochemistry: partial correlation coefficients as a means of identifying parametric relationships and Spearman correlation coefficients for nonnumeric values in determining differences in the composition between oils of different structures and from different territories or stratigraphic plays.