Two Zr−Ce (1:1 molar ratio) mixed oxide specimens, made by the same microemulsion method from different cerium precursor salts (samples ZC1 and ZC2), have been studied by a combination of physicochemical techniques. After calcination at 773 K (high surface area materials HS: SBET = 96 ± 1 m2 g-1) both samples present similar characteristics in XRD, Raman and TEM (pseudocubic phase t‘ ‘), and XPS/Ar+-etching experiments. This latter evidence for those materials gives a similar moderate surface enrichment in cerium and a surface anion vacancy concentration (judged from O(1s) peak shifts) lower than in CeO2; the latter effect suggests an easy diffusion of vacancies to bulk or subsurface regions. Only EPR of adsorbed superoxide species detects a difference between both samples, evidencing in ZC2−HS the presence of small, more reducible Ce-rich bidimensional patches over a Zr-richer substrate. According to XPS/Ar+ etching profiles, by calcination at 1173 K (LS materials; SBET < 8 m2 g-1), surface segregation o...