A dried (773 K, Ar, Ih) NaH-ZSM-5 sample (Si/Al=20, Na/Al=0.5) showed two sharp O-H vibrations at 3745 cm(-1) (SiOH, terminal OH) and at 3612 cm(-1) [Si(OH)AI, bridged OH], a weak, wide band at 3300-3200 cm(-1) due to H-bonded OH and three characteristic (T-O-T) vibrations at 1268, 975 and 834 cm(-1) due to external asymmetric (v(as)(ext)), internal asymmetric (v(as)(int)) and internal symmetric (v(sym)(int)) stretching lattice vibrations, respectively. The value of 975 cm(-1) obtained here for the charge-sensitive v(as)(int) of the ZSM-5, was in good accordance with earlier results gained for bare Cu+, Cu+-CO or CU2+ containing ZSM-5. The broadening of the 975 cm(-1) band to 1010-990 cm(-1) indicated an incomplete ion-exchange of Hf by Naf obtained during the preparation of NaH-ZSM-5 from H-ZSM-5. Depending on the amount, water markedly influenced almost the whole FTIR spectra of NaH-ZSM-5, increasing more or less the intensities of the v(as)(ext), v(as)(int) and v(sym)(int) bands. At high H2O concentration, the H2O ligands in the aquacomplex completely screened the positive charge of Naf ions. As a result, the perturbation effect on v(as)(int) disappeared, since v(as)(int) blueshifted to 1010 cm(-1). Strongly H-bonded interactions with Fermi resonance and the formation of H+(H2O)(n) was highly suggested by the FTIR spectra at medium and high concentration of H2O, respectively. Even at higher temperatures, a part of silanol OH groups revealed unusually strong interactions with H2O molecules retained probably by the Na+ cations. The 880 cm(-1) band attributed to out-of-plane OH bending mode and the v(as)(int) and v(sym)(int), bands varied in relation to each other, in three different stages.