The use of hydrogen storage based on an adsorption process for cars operating on a fuel cell will be seriously considered when the amount of stored gas is high enough, the tank safe and economically ®iable, and the filling process fast enough. To maximize the storage capacity for rapid filling, it is necessary to minimize heating of the adsorbent bed and to imagine means to extract energy toward the outside. Numerical simulation of such a hydrogen storage tank, based on a 2-D model where mass and thermal energy balances are coupled, is presented. Results from simulations agreed well with experiments, when ®arious modified parameters were calculated. Solutions for impro®ing adsorbent beds for hydrogen storage tanks are then proposed.