The adsorption of NO has been investigated in the temperature range 50-150 degrees C on Cu-ZSM-5 and La-Cu-ZSM-5 also in the presence of water and O-2 in a continuous flow reactor. TPD experiments have been performed after each adsorption test monitoring all desorbed NOx species. Water has been found to displace NO from copper sites strongly reducing its adsorption except for nitrate-like species which are partially preserved also in the presence of water. O-2 addition, although decreasing NO adsorption, limits the negative effect of water. Lanthanum co-exchange results in improving the NO adsorption capacity of the zeolite both in the absence and in the presence of water. (c) 2012 Elsevier B.V. All rights reserved.