The reaction of SO2 with polycrystalline Zn and ZnO surfaces has been investigated using synchrotron-based high-resolution photoemission spectroscopy and ab initio self-consistent-field calculations. The chemistry of SO2 on Zn surfaces is quite complex and depends on both the temperature of adsorption and the SO2 exposure. At 300 K, SO2 dissociates on a clean Zn surface to form atomic sulfur and atomic oxygen (SO2,gas --> S-a + 20(a); SO2,gas --> SOgas + O-a). The Zn <-> SO2 bonding interactions induce a significant weakening of the S-O bonds. The theoretical calculations suggest the eta(2)-O,O and eta(2)-S,O bonding conformations of SO2 as the two possible precursors for the dissociation of the molecule. The dissociation reactions are much more exothermic than the formation of SO3 or SO4 : SO2,gas + nO(a) --> SOx, where x = 3 or 2. At high SO2 exposures (300 K), when most surface sites are blocked and dissociation of SO2 cannot occur, SO3 and SO4 are formed on the Zn surface. Adsorption at 100 K suppresses the SO2 dissociation completely, and SO3 is formed through the disproportionation reaction 2SO(2,a) --> SOgas + SO3,a. Zn shows a much higher reactivity toward SO2 than late transition metals. All the results for the reaction of SO2 with ZnO surfaces indicate oxygen to be the active site. The Zn-O bonds in ZnO substantially reduce the electron density of zinc, the metal centers become poor electron donors for pi-back-donation into the LUMO of SO2, and the molecule mostly bonds to the oxygen sites of the oxide surface. Dosing SO2 on ZnO at 300 K results in the formation of surface SO4 species, which are stable to temperatures above 500 K. Results from the ab initio SCF calculations indicate that SO2 adsorbs on an oxygen site to form SO3, which then reacts with a lattice oxygen atom to form SO4. The last step in this process has a substantial activation energy, and after dosing SO2 to ZnO at 100 K a mixture of SO3 and SO4 is produced on the surface.