The use of spectroscopy combined with mathematical data processing made it possible to resolve a wide variety of applied problems related to determination of various characteristics of petroleum products with diffraction spectral analyzers. Examined were several absorption ranges, the region of fundamental transitions at 3000-4000 nm in which hydrocarbons are characterized by high values of the absorption coefficient and the overtone regions at 1800-2500 and 850-1600 nm in which the absorption by different hydrocarbon groups is well resolved. The efficacy of the spectrophotometric technique used for the determination of the parameters of petrochemicals was experimentally confirmed.