First principles electronic structure calculations are applied to styrene lines on a Si(l 0 0) surface grown via a recently reported 'self-directed' growth process. It is found that the delocalized x states of the molecule lie at the bandedge of the valence band, which makes them potentially suitable as carrier channels for hole transport along the styrene line. By contrast, the unoccupied pi* states are situated well above the bandedge of the conduction band. In this case electron transport along the lines seems highly improbable. Finally, scanning tunneling microscope (STM) topographies of occupied states are simulated within a perturbation approach. While the experimental result of vanishing corrugation for the molecule at low bias voltages cannot be accounted for, good agreement is obtained between experiments and simulations for voltages below -2 V. (C) 2002 Elsevier Science B.V. All rights reserved.