The epitaxial growth of fluorine-substituted vanadylphtalocyanine (FxVOPc; x = 15.4) on KBr, KI, and Rbl was Studied. The lattice structure of F15.4VOPC changes from (root 10 x root 10)R +/- 27 degrees to (root 8 x root 8)R0 degrees as the lattice constants of the substrates increase. This sequence is different from that of other shuttlecock - shaped phthalocyanines(Pcs) such as VOPc, TiOPc and AIPcCl. in which the structure changes from (root 10 x root 10)R +/- 27 degrees to (3 x 3)R45 degrees. The difference suggests that the orientation of molecules on the substrates plays an important role in the determination of the lattice structure of F15.4VOPc on alkali-halide substrates.