The effect of phosphorus on molybdenum oxynitrides and oxygen-modified carbides has been studied. Phosphorus was introduced via heteropolyanions. Catalysts were characterized by elemental analysis, X-ray diffraction, N-2 BET surface area, CO chemisorption, and X-ray photoelectron spectroscopy (XPS). XPS measurements show higher concentrations of lower Mo oxidation states on P addition to molybdenum oxynitrides. Two types of phosphorus were revealed by XPS spectra: phosphatelike at about 134 eV, and phosphide at 130 eV. Propene hydrogenation was used to probe the activity of the doped materials. Reactivity experiments over P-containing oxynitrides and oxygen-modified carbides show enhanced hydrogenating properties, in particular for the oxynitride materials. Turnover rate was studied as a function of P content.