The electronic states in the conduction and valence bands of quantum wires are studied by means of the effective mass hamiltonian and the Luttinger hamiltonian. The band mixing effects due to the wire geometry are fully taken into account by an accurate finite element solution of the resulting Schrodinger equations. The quantum wire profiles measured by transmission electron microscopy are used. The comparison of theoretical results with photoluminescence excitation spectra of various nanostructures yields a good agreement and, thus, demonstrates the usefulness of the model in terms of general spectral absorption shapes as a function of wire dimensions and light polarization. Finally, the coupled states of a double quantum wire structure demonstrating simultaneous electron and hole coupling are investigated. Efficient hole tunneling is predicted due to the ubiquitous role of valence band mixing. (C) 1998 Elsevier Science B.V. All rights reserved.