The effect of the kind of ruthenium precursor {Ru₃(CO)₁₂ or RuCl₃·nH₂O} and the activation conditions on the performance of Ru/MgF₂ preparations in thiophene hydrodesulfurization has been studied. The highest activity, higher than that of the commercially available system CoMo/Al₂O₃, was revealed by the Ru/MgF₂ catalyst sulfided in the 50% H₂S/He atmosphere. According to the results of TPR study, this preparation was characterized by exceptionally high content of RuS₂, which seems to be responsible for its high activity. As follows from the product distribution of thiophene HDS, the activation in the H₂S/He atmosphere mainly leads to the formation of saturated products (butane), while the activation in the atmosphere of H₂S/H₂, to the formation of unsaturated products (butene-1, cis- and trans-butene-2).