The selective catalytic oxidation of styrene with hydrogen peroxide was studied over Co-ZSM-5 catalysts which differ in the preparation methods. The catalysts were obtained from NH4+-ZSM-5 by wetness impregnation and ion-exchange techniques followed by different post-thermal treatments: oxidation and reduction. The characterization of acidic properties by FTIR of adsorbed pyridine revealed that new and strong Lewis sites (1452 cm(-1)), different from those characteristics of aluminum in the matrix (1456 cm(-1)) were generated by cobalt introduction. Styrene conversion shows an important increment over the exchanged samples as compared to the impregnated ones. This behavior may be explained by the high Lewis acid sites concentration. Benzaldehyde was the main product in all the samples under study. The samples' magnetic properties were improved with the cobalt incorporation and the applied thermal treatments. The catalytic and magnetic properties of Co-ZSM-5 samples are discussed. (c) 2008 Elsevier B.V. All rights reserved.