DC-conductivity in the p-sexiphenyl films deposited on glass substrate was investigated at temperatures between 10 and 300 K. The thickness of the films was changed between 0.2 and 2.5 mum. Molecular dynamics simulations as well as quantum chemical calculations have shown that there exist at least three different parts of films effectively contributing to the observed features of DC-conductivity: proper crystalline states, amorphous-like inter-grain regions and grain boundaries interfaces. Comparing the experimental data and theoretically calculated dependences we demonstrated that main contribution to the observed DC-conductivity properties give interfaces situated on the borders between polycrystalline grains and amorphous-like substrate, though the latter possess relatively low part of the total film volume. Comparison with the N-phenyls films possessing less number of aromatic rings indicates on a crucial role of aromatics in the observed structural and optical properties. (C) 2004 Elsevier B.V. All rights reserved.