The catalytic activity of CeO2 for soot oxidation under NO/O-2 in loose and tight contact was investigated. Reactivity tests were carried out in a fixed bed reactor set in a vertical electrical furnace and connected to specific gas analyzers for NO, NO2, CO and CO2. Kinetic parameters, such as activation energy and frequency factor, corresponding to the oxidation of soot in catalyzed or non-catalyzed tests were determined by multivariate non-linear regression. The selected method is based on contracting sphere model. The obtained kinetic parameters are in agreement with the mechanism proposed in the literature for soot oxidation assisted or not by NOx. Obtained values confirmed the effect of the catalyst-soot contact on the CeO2 activity. (C) 2012 Elsevier B. V. All rights reserved.