The reversibility of metal-support interaction effects in NM/CeO2 catalysts (NM: Rh, Pt) is investigated using high-resolution electron microscopy and electron energy loss spectroscopy. Reoxidation treatments at 773 K followed by a mild reduction at 473 K are not effective in recovering ceria-based systems from the decorated or alloyed states observed upon high-temperature reduction (T-red > 973 K).