Using pulsed laser excitation, and focusing on multilayers, the photochemistry of SO2 adsorbed on Ag(lll) has been studied by time-of-flight mass spectrometry, complemented by temperature-programmed desorption and Auger electron spectroscopy. At 193, 248, and 351 nm, irradiation of multilayers, but not of monolayers, leads to reactions that break sulfur-oxygen bonds. Photochemistry in the multilayer tracks the SO2 absorption. At 437 and 500 nm, where SO2 does not absorb, no dissociation products (O, SO, or SO3) were detected during (time-of-flight) or after (temperature-programmed desorption and Auger electron spectroscopy) irradiation. Only 193-nm photons induce unimolecular bond dissociation, whereas parent desorption and a bimolecular photoreaction are evident at three wavelengths (193, 248, and 351 nm). The translational energy distributions of the photochemical products vary with wavelength, in general, shifting to higher energies with increasing photon energy. The excitation mechanism and possible primary photochemical processes are discussed.