Organotin oxo cage compounds have an electronic absorption band in the UV spectral range (λmax ~220 nm) associated with a σd electronic transition. Irradiation at 225 nm of thin films of these materials leads to loss of carbon, as shown by X-ray Photoelectron Spectroscopy. Photolysis of solutions of the compounds causes a decrease and slight broadening of the absorption band, consistent with replacement of the organic groups. Quantum chemical calculations support the breaking of the tin-carbon bonds as the primary process, both in electronically excited states and in oxidized states that can be expected to be the result of EUV photoionization.