Thermoelectric characteristics of a newly discovered commensurate (q=0.5) misfit-layered oxide, [Bi2Ba1.8Co0.2O4 +/-omega](q)CoO2, have been significantly enhanced through partial Pb-for-Bi substitution: such substitution is found not only to reduce electrical resistivity and extend the temperature range for metallic conductivity, but also to raise the Seebeck coefficient. To obtain heavily Pb-substituted samples (up to 20-30% substitution level) requires careful control of both temperature and oxygen partial pressure during synthesis. Upon increasing Pb content, the lattice gets shrunken along the layer-piling (c-axis) direction, while the q value remains constant at 0.5. (c) 2005 Published by Elsevier B.V.