The electronic absorption spectroscopy of Ru(II) polyimine complexes, potentially photolabile under visible light irradiation, is investigated by means of density functional theory. The structures of [Ru(phen) 2 (bpy)] 2+ , [Ru(phen) 2 (dmbp)] 2+ , [Ru(tpy)(phen)(CH 3 CN)] 2+ and [Ru(tpy)(dmp)(CH 3 CN)] 2+ (phen=1,10-phenanthroline; bpy=2,2′-bipyridine, tpy=2,2′; 6′,6″-terpyridine, dmbp=6,6′-dimethyl-2,2′-bipyridine, dmp=2,9-dimethyl-1,10-phenanthroline) have been optimized at the DFT(B3LYP) level. The main features of the theoretical absorption spectra of the four molecules have been determined by means of time-dependent DFT (TD-DFT) calculations. The electronic spectra are characterized by a high density of states between 550nm and 350nm assigned mainly to metal-to-ligand-charge-transfer (MLCT) states corresponding to electronic excitations to the low-lying π* orbitals, either localised on the phen, dmp and tpy ligands, or delocalised on the phen/bpy, phen/dmbp, phen/tpy and dmp/tpy ligand. The theoretical spectra of [Ru(phen) 2 (dmbp)] 2+ and [Ru(tpy)(phen)(CH 3 CN)] 2+ reproduce rather well the large bands observed experimentally at about 449nm and 455nm with a blue shift of 0.2eV in the latter case. Four 1 MLCT states (dRu→πphen∗,πphen/dmbp∗) calculated at 445nm, 436nm, 423nm and 418nm with significant oscillator strengths contribute to the band centred at 449nm in the spectrum of [Ru(phen) 2 (dmbp)] 2+ , whereas three 1 MLCT states (dRu→πphen∗,πphen/tpy∗) calculated at 419nm, 378nm and 374nm contribute to the band observed in the spectrum of [Ru(tpy)(phen)(CH 3 CN)] 2+ . The theoretical spectrum of [Ru(phen) 2 (bpy)] 2+ does not differ drastically from the spectrum of the analogous dmbp species with four intense, slightly blue-shifted 1 MLCT (dRu→πphen∗,πphen/bpy∗) states, calculated at 432nm, 429nm, 408nm and 395nm. The theoretical spectrum of [Ru(tpy)(dmp)(CH 3 CN)] 2+ is more compact with close-lying 1 MLCT states (dRu→πtpy/dmp∗,πdmp∗,πtpy∗) calculated at 428nm, 424nm and 416nm with rather small oscillator strengths. The four complexes are characterized by the presence of potentially dissociative metal centred ( 3 MC) excited states between 400nm and 350nm.