The role of La doping with different content in the structure of Ce0.2Zr0.8O2 solid solution (CZ) and the effect of modification on the catalytic activity of supported Pd-only three-way catalysts (TWCs) are clarified. The characterization results reveal that the introduction of La into the lattice of CZ is facile. Zr is replaced by the doped La firstly at low doping content and then Ce is substituted further with increasing la content. The substitution occurs in the bulk preferentially, and then in the surface. The addition of La results in preferable thermal stability, higher BET surface area and enhanced oxygen storage capacity (OSC) compared with CZ, due to the structure modification. La doped fresh samples are beneficial to the conversion of NO and the corresponding aged samples exhibit higher activity for the conversion of all the target pollutants. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.