The effect on combustion in air of the nature of the coke deposited in HZSM5 zeolites used in the MTG process has been studied. This coke is highly hydrogenated and unstable, and its WC ratio decreases during combustion or when a previous thermal treatment is carried out. Coke H/C ratio greatly affects its reactivity during combustion; consequently, a severe thermal equilibration treatment is recommended for reproducibility of results. Combustion kinetics of equilibrated coke, when it is released from the catalyst, has been proven to be similar to that of the coke deposited on other catalysts for several processes. Lower coke reactivity for aging and combustion, on being deposited within the HZSM5 zeolite, must be attributed to air-coke contact restrictions due to the location of the coke, which partially impedes the now of air into the crystals.