TPO (temperature-programmed oxidation), TPSR (temperature-programmed surface reaction), and TPH (temperature-programmed hydrogenation) techniques are used to investigate carbonaceous deposition on Mo/HMCM-22 catalysts for methane aromatization. Different carbonaceous species and their amounts are distinguished. There are at least three kinds of cokes: carbidic carbon in molybdenum carbide, molybdenum-associated coke, and aromatic-type cokes on acid sites. It is suggested that the aromatic-type cokes on Bronsted acid sites are responsible for catalyst deactivation. Catalytic activity can be restored after temperature-programmed hydrogenation.