Synthetic zeolite ZSM5 and its copper forms containing N,N-dimethylethylenediamine (dmen) have been investigated by CHN, energy dispersive spectroscopy (EDS) analysis, X-ray powder diffractometry, X-ray photoelectron spectroscopy and continuous waves hydrogen nuclear magnetic resonance (CW H-1 NMR) spectroscopy. Thermal properties have been studied by methods of thermal analysis-TG, DTA and DTG in the temperature range 20-1000 degrees C in air atmosphere. Mass spectroscopy method was used for the study of the released gas products of thermal decomposition. The results of thermal analyses of two zeolitic samples Cu-ZSM5 and Cu(dmen)(x)ZSM5 (x depends on the mode of preparation) demonstrated their different thermal properties. The main part of the decomposition process of the samples Cu(dmen)(x)ZSM5 occurs at considerably higher temperatures than the boiling point of dimethylethylenediamine, proving strong bond and irreversibility of dmen-zeolite interaction. According to the results of mass spectroscopy the decomposition process in inert atmosphere is characterized by the development of a large spectrum of products with atomic mass from 18 to 447 atomic mass units as a consequence of the catalytic effect of the silicate surface. (C) 2006 Elsevier B.V. All rights reserved.