In this work, three catalysts with different chemical and physical properties were synthesized (one HZSM-5 zeolite and two ordered mesoporous aluminosilicates-MCM-41a and MCM-41b) and tested for the pyrolysis of four samples of commercial polymers (LDPE, PP, PS and EVA copolymer), using a thermobalance under nitrogen atmosphere at a heating rate of 10 degrees C/min. The catalysts were characterized using X-ray powder diffraction, nitrogen adsorption at 77 K and Al-27 and Si-29 solid state nuclear magnetic resonance (NMR). The HZSM-5 zeolite showed the lowest activity in the catalytic pyrolysis of the four polymers. The two mesoporous catalysts, with a greater pore size, were the most active materials in the catalytic pyrolysis of the polymers, and the MCM-41b sample, with higher acidity, was the most active. The presence of MCM-41 samples during the pyrolysis of the high impact PS sample permits us to distinguish between different decomposition steps which are probably related to the pyrolysis of PS and polybutadiene domains. This processes separation was not observed in absence of the catalyst. Thus, catalytic pyrolysis of such samples in the presence of MCM-41 and other catalysts could be a promising technique to characterize this type of polymers. (c) 2005 Elsevier B.V. All rights reserved.