The electrochemical oxidation of 2,3-2,4-and 2,5-diaminophenol, on platinum electrode, in acid medium was studied using cyclic voltammetry, in situ UV–vis and in situ FTIR spectroscopies. The spectroscopic data indicates that 2,4-diaminophenol suffers hydrolysis giving the formation of 2-amino-hydroquinone/2-amino-p-benzoquinone in solution. The oxidation mechanism of 2,5-diaminophenol is similar to the p-phenylenediamine giving 2-hydroxy-p-benzoquinoneimine and its hydrolysis product, 2-hydroxy-p-benzoquinone. The electrochemical results suggest that 2,3-diaminophenol generates a non-electroactive polymeric material on the electrode surface.