The dependence of substrates on the epitaxial relationship of vapor deposited thin films p-sexiphenyl (p-6P) was investigated by X-ray diffractmetry. The cleaved (001) surfaces of single crystals of NaCl, KCl and KBr were used for the substrate. The temperature dependence of the film structure was also examined between 50degreesC and 170degreesC. The epitaxial relationships of both standing and lying orientations were determined for the films grown on each substrate. The observed complex patterns of in-plane orientations were explained in terms of misfit ratio.