In order to consider some drawbacks that avoid obtaining diesel and gasoline with ultra-low sulfur concentration, inhibition by quinoline and solvent effects on dibenzothiophene (DBT) hydrodesulfurization (HDS) were evaluated in this work. Reaction results without quinoline indicated that solvents such as: n-heptane (gasoline model) and n-hexadecane (diesel model) affected the reaction rate. According to a Langmuir-Hinshelwood model, K_DBT/K_solvent values showed that adsorption of DBT on the catalyst was more important than that of the solvent. This solvent/DBT competition for the active sites on the catalyst was more notorious in the gas phase (n-heptane) than in the liquid phase (hexadecane) reactions. Furthermore, selectivity depended on the solvent: direct desulfurization pathway was favored in n-hexadecane. The inhibition factor data indicated that quinoline inhibition was similar for both solvents. The rate of Dibenzothiophene hydrodesulfurization was affected mainly by quinoline inhibition, regardless of the phase at which the reaction took place.