Nanostructured CeO₂–ZrO₂ mixed oxides have attracted great interest in the past 10 years, in particular as redox or oxygen storage promoters in the three-way catalysts. However, it has now became clear that both the chemistry of the simple oxides and the complex metal–CeO₂-based oxide interactions can play a critical role in developing novel and highly active materials for a number of processes, ranging from catalysts for H₂ production from fuels up to ceramic materials and solid state conductors for fuel cells. Despite the apparent simplicity of these systems, extreme variability of their chemical and textural properties has been observed. An attempt is made here to rationalise the various factors and the inter-connections to the structure, the texture, and the effects of the nanometre scale, which all contribute to the properties of these materials.