The condensed-phase excited-state reaction dynamics of chlorine dioxide are investigated using resonance Raman intensity analysis. Absolute Raman intensities are measured on resonance with the 2B2–2A2 electronic transition and used to establish the excited-state structural evolution which occurs on the 2A2 surface following photoexcitation. Analysis of the intensities demonstrates that excited-state relaxation occurs along all three normal coordinates; however, only modest evolution is observed along the asymmetric stretch. This limited relaxation stands in contrast to the extensive motion along this coordinate in the gas phase. It is proposed that the initial excited-state structural relaxation serves to define the symmetry of the reaction coordinate and thus the mechanism of Cl production following photolysis of OClO.