Pd(II) and Pt(II) new complexes with simple aromatic diamines were synthesised and characterised with the aim of studying their possible antitumour activity. The aromatic diamines chosen were 2,3-diaminotoluene (2,3 dat), 3,4-diaminotoluene (3,4 dat), 4,5-diaminoxylene (4,5 dax) and 2,3-diaminophenol (2,3 dap). The complexes, of formulae cis-[MCl(2)(diamine)], were characterised by elemental analysis, conductivity measurements, 1H, 13C(1H) and 195Pt NMR spectroscopy. The X-ray crystal structure was also resolved for the palladium complexes with 2,3-diaminotoluene and 4,5-diaminoxylene. The DNA adduct formation of the eight new complexes synthesised was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by the complexes on plasmid DNA pBR322 were also obtained. Values of IC50 were also calculated for the four platinum complexes against the cisplatin resistant tumour cell line A2780cisR.