A series of Nb- and NbCo-containing mesoporous catalysts with variable Nb/Si molar ratios and a highly ordered hexagonal arrangement of the pores have been hydrothermally synthesized from sodium silicate or tetraethylortosilicate. The prepared materials were characterized by various techniques, such as: X-ray diffraction (XRD), N-2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The oxidizing character of the Nb- or NbCo-MCM-41 materials was revealed in the selective oxidation of styrene, benzene and toluene with H2O2 in liquid phase. A kinetic study was realized for oxidation of styrene with Nb-MCM-41 catalysts. All the Nb and NbCo modified mesoporous catalysts were very active in oxidation of styrene with H2O2. (C) 2003 Elsevier Science B.V. All rights reserved.