The use of catalysts to improve the performances of water treatment technologies is well known; in the last years more scientific attention was given to the treatment of the olive oil mill wastewaters. This problem affects especially the Mediterranean area because this region is the largest world olive oil producer. In this paper, the results of the wet hydrogen peroxide catalytic oxidation on olive oil mill wastewaters using Fenton-like type catalysts (Cu-Silicalite-1 and Cu-pillared clay) are presented. Both the catalysts showed a high conversion in the oxidation of poly-phenols and were able to drastically reduce the chemical oxygen demand, the biochemical oxygen demand and the non-biodegradability of the olive oil mill wastewaters. (C) 2007 Published by Elsevier B.V.