Nickel-tungsten sulfide catalysts for the hydrogenation and hydrodesulfurization of aromatic hydrocarbons are synthesized by the in situ decomposition of thio salts using different methods: the in situ decomposition of a [BMPip](2)Ni(WS4)(2) precursor in an ionic liquid, the in situ decomposition of a [BMPip](2)Ni(WS4)(2) precursor in a hydrocarbon feedstock, the in situ breaking of a SPAN-80 surfactant-stabilized suspension of solid Ni/(NH4)(2)WS4 precursor particles in a hydrocarbon feedstock, and the decomposition of oil-soluble precursors (tungsten hexacarbonyl and nickel(II) 2-ethylhexanoate) in a hydrocarbon feedstock. The resulting catalysts are characterized by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy; their catalytic activity is studied in a batch reactor using the example of the hydrofining of light cycle oils with different compositions.