The catalytic activity of TiO 2 , ZrO 2 , and CeO 2 for soot oxidation under NO x /O 2 was compared. Characterisation of the oxides by N 2 adsorption at −196 °C, Raman spectroscopy, and XRD revealed that the predominant crystalline phase of TiO 2 (rutile or anatase) and ZrO 2 (monoclinic or tetragonal) had no significant affect on the catalytic activity of these oxides for soot oxidation with NO x /O 2 . CeO 2 , with the only allowed fluorite structure, is the most active oxide because accelerates the NO conversion to NO 2 , whereas TiO 2 and ZrO 2 do not catalyse this reaction. Once NO 2 is produced by CeO 2 , part of it reacts with soot, and a certain amount is stored on CeO 2 . NO x stored on CeO 2 under reaction conditions (around 450 °C) does not accelerate soot oxidation and can be evolved under N 2 flow but not under a NO x /O 2 stream. NO x storage on TiO 2 and ZrO 2 under reaction conditions was not detected. An additional benefit of CeO 2 with regard to TiO 2 and ZrO 2 is that the CeO 2 -catalysed soot oxidation yields mainly CO 2 , whereas TiO 2 and ZrO 2 yield higher percentages of CO. This can be attributed to the lowest CeO 2 -catalysed soot oxidation temperature and to the ability of CeO 2 to catalyse CO oxidation to CO 2 . The effect of thermal sintering at 800 °C (decreased BET surface area and increased crystal size) on CeO 2 is more important than on TiO 2 and ZrO 2 , but 800 °C-calcined CeO 2 is still more active for soot combustion than the other oxides studied.