The present work has been led to verify the influence of some physicochemical properties of carbon supports on the catalytic behaviour of hydrotreatment catalysts. The catalytic conversion of ethylene in presence of hydrogen was carried out at 300degreesC on Mo, Ni and NiMo catalysts supported on two different activated carbons (AC). The results were interpreted in terms of the hydrogenating/hydrogenolytic activity, catalytic stability and coking functions of catalysts. Changes observed both in activity and evolution of products as function of the final temperature of two reducing pretreatments indicate that H-type carbon-supported NiMo catalysts has much more tolerance to coke deposition and therefore they are less prone to suffer deactivations than catalysts based on L-type AC. The apparent rate constants and the initial rates of coke formation were estimated indirectly as an attempt to provide a better understanding the influence of chemical surface functionalities and of textural properties of AC. A correlation was found between these kinetic parameters of coke formation and the catalytic behaviour of catalysts. The results were compared with respect to a conventional alumina-supported NiMo catalyst indicating that using H-type AC as a support of hydrotreatment Ni-consisting catalysts we can be able to maintain high activities over longer periods of operation, at least, for the hydrogenation of simple insaturated hydrocarbons such as ethylene.