This paper reviews the photochemical PtC bond homolysis reactions of metalcarbon bonded platinum compounds. Three types of complexes are considered: [Pt(R) 2 (COD)], [Pt(R) 2 (α-diimine)] and [Pt(Me) 4 (α-diimine)]. This photoreactivity originates in the involvement of the σ-bonded co-ligands in low-lying excited states. This involvement was proved by time-dependent density-functional theory (TD DFT) calculations and resonance Raman (rR) spectroscopy. In the case of the platinum(II) complexes, the contribution of the co-ligand to the high-lying filled orbitals increases with increased σ-donor strength of this ligand. Concurrently, the photoreactivity increases dramatically in the case of the [Pt(R) 2 (COD)] complexes. The corresponding α-diimine analogues are much less reactive due to the smaller co-ligand participation in high-lying filled orbitals. The platinum(IV) complexes [Pt(Me) 4 (α-diimine)] are very photoreactive, due to the fact that the HOMO has almost exclusively σ(C ax PtC ax ) character.