The phase compositions of molybdenum sulfide-based catalysts with various S/Mo ratios which are synthesized ex situ from reverse emulsions of the aqueous solution of ammonium paramolydbate (NH4)(6)Mo7O24. 4De(2)D in the medium of vacuum residue in the presence of a sulfiding component (sulfur) are studied by chemical thermodynamics and X-ray diffraction. Issues related to the interpretation of the phase composition determining properties of the catalysts are discussed in detail. It is shown that the catalyst predominantly comprising MoS2 is formed at S/Mo above 2.5 (mol/mol) in the reverse emulsion and the content of carbon-containing components adsorbed on DeD 3/4 -containing particles grows with an increase in the degree of sulfiding.