With large countries as India and China in tremendous development accompanied by a growing worldwide population, questions arise in how energy demands can be met in the post-oil society. The methanol-to-hydrocarbon process, catalysed by Brønsted acidic zeolites, constitutes an alternative route for the production of gasoline and other valuable hydrocarbons from feedstocks such as natural gas and coal. Catalyst deactivation by coke formation is nevertheless a big concern, and a better understanding of this process is of utmost importance with respect to both economical and environmental concerns. The deactivation by coke formation is studied over the medium and large pore zeolites H-ZSM-22, H-ZSM-5, H-Beta (two) and H-mordenite at a reaction temperature of 400 °C and WHSV = 2.00 h-1. Gradually deactivated zeolites have been investigated with gas adsorption measurements, thermogravimetry and coke analysis by dissolution and extraction with subsequent chromatography. Large differences in catalyst lifetime was observed with rapid deactivation of H-mordenite and H-ZSM-22, compared to H-beta and the archetype H-ZSM-5. A broad distribution of polycyclic arenes was observed as retained coke species in gradually deactivated samples of both H-ZSM-22 and H-ZSM-5. This is in contrast to earlier observations done for H-ZSM-5, and might shed some light on the assumption of coking exclusively on the external surface of this catalyst at normal reaction temperatures. GS-MS/FID analyses have been applied in a quantitative manner, but only H-ZSM-22 showed high relative amount of soluble coke, with a maximum of 60 % after 30 minutes time on stream. Only small amounts were detected for the large pore H-mordenite and beta zeolites and, it is believed that deactivation is caused by coking from larger graphitic species for these materials.