This article analyzes the schemes of reactor blocks of industrial diesel hydrotreating plants. It is shown that all variants of industrial direct-flow hydrotreating reactor plants are equivalent in terms of the required volume of the catalyst. A new model of hydrotreating raw materials is given, which considers raw materials as a complex or set narrow fractions, each of which contains a conditional organosulfur pseudo-component. The concentration of total sulfur in pseudo-components is equal to the sum of the concentrations of the aggregate or lump of organosulfur impurities in total sulfur in the corresponding narrow fraction. Based on this model, the principle of differentiated hydrotreating of diesel fuel and new schemes of reactor blocks of diesel hydrotreating plants were developed. Mathematical modeling and optimization of differential hydrotreatment were performed. The new schemes will reduce the amount of catalyst or increase the performance of hydrotreating plants compared to traditional industrial schemes of hydrotreating plants. The basic laws of differential hydrotreating of diesel fuel were formulated.