Density functional theory (DFT) and time-dependent DFT (TD-DFT) provide new insights into the photodegradation pathways of the cytotoxic complex cis,trans,cis-[Pt(N(3))(2)(OH)(2)(NH(3))(2)] allowing assignment of (1)LMCT transitions in the visible region of the UV-Vis spectrum; upon excitation to these low-energy (1)LMCT states, release of one N(3)(-) ligand is facilitated, and on triplet formation, the dissociation of both NH(3) and N(3)(-) groups trans to each other is promoted with no apparent reduction of the Pt(IV) centre.