The voltammetric behaviors of dihydroxybenzene isomers were studied at an ordered mesoporous carbon-modified glassy carbon (OMC/GC) electrode. Compared to the bare electrode, the electrocatalytic activity of the modified electrode toward dihydroxybenzenes is evidenced by the increase of the peak current and the decrease of the peak separation (Delta E (p)) in 0.1 M pH 5.0 phosphate buffer solution (PBS). Furthermore, at the OMC/GC-modified electrode, the three isomers could be separated entirely. The oxidation peak potential difference between hydroquinone and catechol is 154 mV, whereas that difference between catechol, and resorcinol is 370 mV. In the amperometric detection, the peak currents of dihydroxybenzene increased linearly with increasing dihydroxybenzene contents. The detection limits were 7.6 x 10(-8) M, 1.0 x 10(-7) M, 9.0 x 10(-8) M for hydroquinone, catechol and resorcinol, respectively, which are the lowest values ever reported for dihydroxybenzene isomers. These make OMC/GC electrode a promising candidate for the simultaneous determination of isomers.