The effects of chemical composition, calcination temperature, and the addition of potassium on the physicochemical properties and reactivity of MnCeOx systems in the catalytic wet oxidation (CWO) of phenol with oxygen (TR = 373 K; PR = 1.0 MPa; w(cat)/w(phenol) = 5) have been addressed. Characterization data of "fresh" and "spent" catalysts signal the occurrence of a typically heterogeneous reaction path, the surface reaction between the adsorbed intermediate(s), and activated oxygen species being the rate-determining step (rds). Basic relationships among structural properties, the redox pattern, and CWO activity provide evidence of the main catalyst design requirements. A new synthesis route based on the redox-precipitation reactions of various Mn and Cc precursors then yields MnCeOx catalysts with improved physicochemical features and superior CWO activity, in comparison to conventional coprecipitated systems.