Comparison of palladium catalysts (1 wt % Pd) based on nanodiamonds and activated carbon in the liquid-phase hydrogenation of organic compounds of different nature (some aromatic nitro compounds, unsaturated hydrocarbons, alcohols, and acids) under mild conditions (T = 318 K; = 0.1 MPa; solvent, ethanol) has been conducted. It has been found that the palladium catalyst based on nanodiamonds is more active in the hydrogenation reaction and more sensitive to a change in the nature of the substrate than its counterpart based on activated carbon.