Comparative scanning tunneling microscopy (STM) studies of 4-n-hexyl-4’-cyanobiphenyl (6CB) and 4-n-octyl-4’-cyanobiphenyl (8CB) layers on graphite and on beta-Nb3I8 demonstrate the dependence of the adsorbate structure on the substrate nature. Whereas areas with differently oriented linear features assigned to crystal-like arrays of extended nCB molecules are formed on graphite, domains of two types-including one with a large hexagon structure (a = 13 - 14 nm) -were observed in the STM images of 6CB and 8CB layers on iodide surface of the beta-Nb3I8 crystal. The orientations of the hexagon- and triangle-shaped domains of these types were different with respect to the crystallographic lattice of the substrate. These findings were explained by the formation of two orientational phases of n-alkyl-cyanobiphenyls. The phases were independent of the temperature in the range from + 15 to + 50-degrees-C, where transitions in the bulk state occur. The molecular-scale STM images of 6CB and 8CB adsorbates on beta-Nb3I8 also reveal periodic features, which were assigned to moire patterns associated with a superposition of the adsorbates and substrate lattices.