Zeolite ZSM-5 of different Si/Al ratio, templated and non-templated ones were modified with iron cations introduced by means of ionic exchange from aqueous solution and by solid state procedure. The modified samples calcined in the range of temperatures from 500 to 1000degreesC were applied for benzene to phenol hydroxylation. Interaction of benzene and N2O oxidant with Fe-ZSM-5 was searched by IR spectroscopy. The acidity of the samples was characterised by means of activity for cumene cracking and by IR spectra of adsorbed pyridine. Some correlations between oxidative activity, rate of deactivation and acidity of iron modified zeolites ZSM-5 were discussed. (C) 2004 Elsevier B.V. All rights reserved.