MgO-supported Mo, CoMo and NiMo sulfide catalysts were prepared by impregnation using slurry MoO3/methanol and solutions of Ni and Co nitrates in methanol. The catalysts exhibited very high hydrodesulfurization activity and low hydrodenitrogenation activity in competitive reactions of thiophene and pyridine. The promotion effect for HDS of Ni and Co was higher for our MgO-supported MoS2 catalysts than for conventional Al2O3-supported catalysts. The specific features in the TEM images of MgO-supported catalysts as compared to conventional Al2O3-supported catalysts were fairly broad MoS2 slab length distribution and the presence of unusually long MoS2 slabs.