Iron ferrierites with low iron content (Fe/Al between 0.018 and 0.072) were used as model catalysts to evaluate the participation of individual iron species, with special interest in the role of iron in beta cationic sites, for formation of active sites for N2O decomposition. Despite low iron content, the catalysts with prevailing iron located in beta sites of two types exhibited high conversions of N2O and activity increase with increase of iron loading. These results indicate formation of the active iron species already at very low concentrations, while at higher concentration level would part of the iron enter also into less active positions. Semi-quantitative analysis of the TOF values of individual iron centers was done using the recently established Mossbauer parameters of the Fe(II) parameters for individual iron cationic species, i.e. beta (beta-1 and beta-2) and alpha sites [1]. The evaluation of the TOF presents a new support for the role of iron in beta sites in N2O decomposition and further indicates similar role of both beta-1 and beta-2 sites in formation of the Fe center dot center dot center dot Fe active site. (C) 2011 Elsevier B.V. All rights reserved.