The paper presents a methodology for the kinetic modeling of hydrodesulfurization of oil fractions. Instead of lumping the S components, these are considered individually. To avoid an untractable number of parameters, a structural contribution approach is applied. This implies relating the rate equations of substituted S-containing components to those of the heads of the family. By way of example, hydrodesulfurization of a light cycle oil on a. commercial CoMo/Al2O3 catalyst was studied in a completely mixed multiphase flow reactor. The surface reaction between adsorbed reactants and two competitively adsorbed hydrogen atoms was the rate-determining step for both hydrogenolysis on sigma sites and hydrogenation on tau sites. Structural contributions were derived for hydrogenolysis and hydrogenation of methyl-substituted benzothiophenes and dibenzothiophenes.