Differently composed mixtures of HDPE and PMMA were pyrolysed at 700 degrees C and 815 degrees C in pyrolysis reactor. It was directly coupled with gas chromatography/mass spectrometry (GC/MS). On line pyrolysis GC/MS was applied in analysis of hydrogen, methane and carbon monoxide yielding in polymer blends pyrolyzate with/without metal (Ni, Co) coated particles, tested as a methane to hydrogen conversion catalysts supporting additives. They were prepared by electrochemical deposition of Ni and Co on the small iron particles surface. Maximum hydrogen production was confirmed at the highest pyrolysis temperature (815 degrees C), and the highest HDPE contents in the blends mixture. Higher content of the PMMA in the mixture led to higher production of CO and lower hydrogen contents in pyrolyzate. Nickel and cobalt containing additives affected production of hydrogen and other components at both 700 degrees C and 815 degrees C pyrolysis temperatures. An effect of different heat distribution between metal particles and polyblends occurred and affected hydrogen production. Application of pyrolysis gas chromatography in hydrogen production from polyblends represents an important tool to model future technological outputs as well simultaneous hydrogen production and CO, CO2 elimination. Moreover, catalysis assisted conversion of methane to hydrogen can improve final hydrogen content in pyrolyzate. Effectivity of pyrolysis hydrogen production was determined by its quantification based on analytical calibration. (C) 2011 Elsevier Ltd. All rights reserved.