The [RhCl 3 (N–N)(DMSO)] complexes, the N–N being 2,2′-bipyridine (1), 1,10-phenanthroline (2), 4,7-diphenyl-1,10-phenanthroline (3), 4,4′-dimethyl-2,2′-bipyridine (4) and 1,10-phenanthroline-5,6-dione (5), have been synthesized and characterized with spectroscopic methods. The compounds 2–5 adopt mer- and complex 1 fac-structure. The molecular and electronic structure studies of mer- and fac-complexes with bpy and phen ligands at the DFT B3LYP level with 3-21G ∗∗ basis set showed that mer-isomers are more stable. The cytostatic activity of the [RhCl 3 (N–N)(DMSO)] complexes against Caco-2 and A549 tumor cells have been studied. Their antibacterial activity have also been investigated. It has been found that the very promising biological activity show complexes 2, 3 and 4.