The elastic scattering Green function theory in combination with density-functional theory is applied for studying electronic transport properties of single 1,4-phenylenediisocyanide molecules sandwiched between two gold electrodes at ab initio level. The special attention is paid to effect of contact configurations between molecule and electrodes on current and conductance characteristics of the molecular junction. Conductive features are shown to be strongly dependent on detailed contact structures. For the contacts formed in tetrahedron-typed configuration, good agreement in conductive features between theory and experiment can be achieved. (c) 2006 Elsevier B.V. All rights reserved.