The nature of vanadium species in V substituted zeolites is determined by combined experimental (XRD, FTIR, DR UV-vis) and theoretical (periodic DFT Calculations) Study. The introduction of V ions in lattice sites of SiBEA zeolite is evidenced by XRD and FTIR spectroscopy. The state of vanadium is characterized by DR UV-vis spectroscopy. The vanadium is incorporated in SiBEA zeolite as tetrahedral V(V) species, containing the V=O double bond and linked by V-OSi bounds to the zeolitic framework DR UV-vis spectroscopy shows that environment of V(V) species depends oil [lie treatment condition of the VSiBEA sample. The calcination/hydration processes allow LIS to distinguish in VSiBEA sample two different kinds of tetrahedral V(V) species, less and more distorted. Further dehydration of this sample allows detecting by FTIR two bands at 3620 and/or 3650 cm(-1) corresponding to the presence of hydroxylated tetrahedral V(V) species, possessing the V-OH group. These O-H groups have acidic Bronsted character as shown by FTIR in the presence of adsorbed pyridine. The V(V) and V(IV) model sites are discussed using periodic DFT calculations. (C) 2008 Elsevier B.V. All rights reserved.