The promotional effect of cobalt oxide on the catalytic performance and the physicochemical properties of Pd only three-way catalysts and Ce0.67Zr0.33O2 mixed oxides (CZ) prepared by co-precipitation and impregnation methods have been investigated. It is worthwhile to note that the role of Co significantly depends on the method of Co doping in the CZ. The introduction of cobalt oxide by co-precipitation exhibits significant influence on the catalytic activity of Pd only three-way catalyst with enhancing textural and structural properties, compared to the introduction of cobalt oxide by impregnation method. Furthermore, CZ doped with cobalt oxide by co-precipitation results in the formation of more homogeneous ternary solid solution, which promotes the metal support interaction between CZ and cobalt metal and improves oxygen storage capacity (OSC) of samples. It also proves that the textural and structural properties of supports can affect the reducibility and oxygen storage capacity of samples at low temperature. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.