We have investigated the effects of the interfacial bond arrangement on the electronic transport features of metal–nanotube–metal systems. The transport properties of finite, defect-free armchair and zigzag single-walled carbon nanotubes attached to Au (111) metallic contacts have been calculated by means of the non-equilibrium Green functional formalism with the tight-binding and the extended Hückel Hamiltonians. Our calculations show that the electrode material is not the only factor which rules contact transparency. Indeed, for the same electrode, but changing nanotube helicities, we have observed an overall complex behaviour of the transmission spectra due to band mixing and interference. A comparison of the two models shows that the tight-binding approach fails to give a satisfactory representation of the transmission function when a more accurate description of the C–C and Au–C chemical bonds has …