X-ray photoelectron spectroscopy (XPS) valence band spectra were used to infer information about the structure of molybdates having different symmetries. Standard. compounds such as sodium molybdate, ammonium dimolybdate, and ammonium heptamolybdate were used as references. It has been verified that XPS valence band measurements can be used to determine the Mo symmetry in physical mixtures of Mo compounds and carbon as well as in Mo/C catalysts. This information was obtained without subtraction of the carbon contribution to the overall valence band envelope. The results show that for Mo/carbon catalysts prepared by equilibrium adsorption at pH 2 and 5 the major Mo surface species is octahedrally coordinated.