The hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4-methyldibenzothiophene (4 M-DBT), 4,6-ditnethyldibenzothiophene (4,6 DM-DBT) and 4,6-diethyldibenzothiophene (4,6 DE-DBT) as real gas oil components on NiMo/Al2O3 catalyst was investigated. On the basis of the first order rate constants of HDS of the individual sulfur compounds calculated by both integral and differential evaluations the reactivities of the investigated compounds decreased in the order DBT >> 4 M-DBT >4,6 DE-DBT approximate to 4,6 DM-DBT. Additionally, results showed that product inhibition during HDS does not take place.