The selective hydrodesulfurization (HDS) reaction of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in decane containing a dominant amount of naphthalene was examined over blends of CoMo/Al2O3 and Ru/Al2O3, and their activity was compared to those of CoMo, NiMo, and Ru/Al2O3 in their single use. The blend exhibited an excellent activity for HDS of 4,6-DMDBT through its selective hydrogenation without excess hydrogenation of the aromatic partner. NiMo/Al2O3 and CoMo/Al2O3 examined in the present study were inferior to the blend for the HDS of 4,6-DMDBT, because the hydrogenation activity of the first catalyst is toward the aromatic partner while the second catalyst is inferior in the hydrogenation activity for 4,6-DMDBT.