The composition of the products of the combined conversion of various naphthenic hydrocarbons and fatty acids has been studied. It was determined that the distribution of the cracking products of model mixtures is largely dependent on the unsaturation of the hydrocarbon chains of fatty acids. It was found that at a content of oleic acid of 5 wt % in the model mixtures the changes in the conversion of cyclohexane, methylcyclohexane and decalin almost do not occur. With increasing the content of the unsaturated fatty acid up to 25 wt % the effect of inhibition of cracking of the hydrocarbons was observed. Upon combined conversion of tetralin and oleic acid a decrease in hydrocarbon conversion was not observed. According to the results of combined transformations of naphthenes with stearic acid it was found that a high content (25 wt %) of a saturated fatty acid in the model mixture does not result in a sharp decrease in the hydrocarbon conversion.