The electrochemical oxidation of 4-tert-butylcatechol (I) and 3,4-dihydroxybenzatdehyde (II) in methanol at various pH values has been studied using cyclic voltammetry and controlled-potential coulometry. The results indicate that in the presence of sodium acetate, 4-tert-butylcatechol (I) undergoes methoxylation according to an ECE mechanism to form the related methoxyquinone (Ic). Under these conditions, 3,4-dihydroxybenzaldehyde (II) participates in a dimerization reaction and, in acidic solution, this compound undergoes a methoxylation reaction parallel to the dimerization reaction to give the related methoxyquinone (IIc).