Cerium oxide-carbon composites were prepared and tested as ozonation catalysts for the removal of two selected carboxylic acids. oxalic and oxamic, and one textile dye (CI. Reactive Blue 5). The results were compared with those obtained in non-catalytic ozonation and ozonation catalysed by cerium oxide and carbon materials (activated carbon, carbon xerogel). With the exception of cerium oxide, a total degradation of oxalic acid was obtained in approximately 90 min for all prepared catalysts and the catalytic activity increases with the amount of carbon present in the composites. Despite of oxamic acid be more refractory to ozonation than oxalic acid, 75% of oxamic acid removal was achieved after 10 h of reaction in the presence of the ceria-activated carbon composite with 90% of carbon material. In the mineralization of the textile dye, the catalytic activity of the composites increases with the amount of activated carbon introduced. (C) 2010 Elsevier B.V. All rights reserved.