Ceria has been prepared by flame spray pyrolysis and tested for activity in catalytic soot oxidation. In tight contact with soot the oxidation activity (measured in terms of the temperature of maximal oxidation rate, T-max) of the flame made ceria is among the highest reported for CeO2. This can to a significant degree be ascribed to the large surface area achieved with the flame spray pyrolysis method. The importance of the inherent soot reactivity for the catalytic oxidation was studied using various soot samples, and the reactivity of the soot was found to have a significant impact, as the T-max-value for oxidation in tight contact with a catalyst scaled linearly with the T-max-value in non-catalytic soot oxidation. The T-max-value in non-catalytic soot oxidation was in turn observed to scale linearly with the H/C ratio of the carbonaceous materials.