The electrochemical behavior of hydroquinone in unbuffered aqueous solution was investigated using cyclic voltammetry. Subsequent cathodic scan showed a new cathodic peak at the negative potential and another similar cathodic peak for catechol. The peak current increased with the increasing pH of the bulk solution and concentration of hydroquinone. We observed that only the new cathodic peak increased, whereas the other peaks remained constant with the addition of quinone to the test solution. This new cathodic peak was caused by the ultrafast diffusion of proton from the electrode surface to the bulk solution. The results can help us understand the unique characteristics of hydroquinone in unbuffered solution.