The hydroconversion of oil distillation residues in the presence of ultrafine catalysts synthesized in the reaction medium from feedstock-soluble iron-containing precursorsiron acetylacetonate, ferrocene, and iron oleateis studied. It is found that the distillate fraction yield and the feedstock conversion in the hydroconversion reaction increase in the following order: iron oleate, ferrocene, iron acetylacetonate. The efficiency of Fe-containing catalysts synthesized from oil-soluble precursors is compared with the efficiency of the nanosized MoS2 catalyst previously studied in the tar hydroconversion process. In the presence of the catalysts synthesized from iron acetylacetonate and ferrocene, the distillate fraction yield and the feedstock conversion are higher than the respective parameters in the case of MoS2. However, with respect to the yield of condensation products (coke), the tested Fe-containing catalysts are significantly inferior to MoS2.