single‐crystal electrodes have been used to study the mechanism of the chlorine evolution/reduction reactions. (110) and (101) surfaces show the same anodic Tafel slopes equal to 40 mV/decade. Significant differences in the electrocatalytic behavior of these two surfaces were found for the chlorine reduction reactions. Two cathodic voltammetric peaks at vs. SCE reference were observed for the (110) electrodes. The peak at is completely suppressed in case of the (101) electrodes. It is suggested that the natural oxygen sites that are available only on the ideal (110) surfaces provide active centers for the formation of surface O.Cl+ groups that are intermediates in the Krishtalik mechanisms. The cathodic LSV peak at observed only for the (110) surfaces indicates, then, the reaction path with chloronium intermediates. The influence of the surface ruthenium oxide rearrangement processes on catalytic activity of the electrode and possible changes in the reaction mechanism are discussed in detail.