The methoxylation of p-tert-butyltoluene (TBT) in CH3OH-H2SO4-H2O soln. has been investigated on graphite and boron-doped diamond (BDD) anodes. Different reaction intermediates have been found on BDD and graphite. In fact BDD electrodes favor the formation of dimeric products under the chosen conditions. This difference has been attributed to a mechanism based on the non-catalytic character of BDD electrodes and to the presence of active functionalities on graphite anode. [on SciFinder (R)]