Meso- or micro/mesoporous supports (NbMCM-41 and NaY + NbMCM-41, respectively) were tested for Pt loading. The effects of the support structure and composition on the metal oxidation and on nitrate storage properties were pointed out in the SCR for NOx removal. Nitrate species were found directly related to the catalytic performance of Pt. Niobium from NbMCM-41 matrix in Pt/NbMCM-41 play the role of NOx storage species, whereas in the presence of NaY in the support, sodium cations act as storage for NO.. (c) 2006 Elsevier B.V. All rights reserved.