This computational study gives an insight into the reactivity of the active sites on the most open Ru(112¯1) surface toward CO adsorption and dissociation. The adsorption sites for the CO molecule on different active sites have been characterized by frequency analysis and are in good agreement with the experimental results obtained from high-resolution electron energy loss spectroscopy (HREELS). Two dissociation paths have been explored where the CO molecule is adsorbed in a preactivated state. The results show that the CO has a barrier of 65 kJ/mol with respect to the adsorbed state. It dissociates at the 4-fold hollow site as predicted by an experimental study. The barrier found for the CO dissociation on Ru(112¯1) surface is significantly lower than that on Ru(101¯5) steps studied earlier.