The activity of unsupported Ni-Mo sulfide catalysts is studied in the hydroconversion of benzothiophene and dibenzothiophenes in the temperature range of 340-380 degrees C and at an increased H-2 pressure and in the C?/H-2? system. The structure of dispersed catalysts formed by the in situ high-temperature decomposition of oil-soluble precursors (molybdenum hexacarbonyl, nickel naphthenate) is investigated by TEM. Effects of C?/H-2? molar ratio, water mass content in the system, and CO pressure on the activity of the catalysts and yields of the products are explored. It is shown that, in the C?/H-2? system, the highest conversion of benzothiophene and dibenzothiophene is attained at a temperature of 380 degrees C, a C? pressure of 5MPa, and a C?/H-2? molar ratio of 2. The introduction of alkyl substituents into a dibenzothiophene molecule causes a reduction in the rate of reaction that predominantly occurs via the hydrogenation of aromatic rings. The catalyst activities in hydrogenation under H-2 pressure and in the C?/H-2? system are comparable.