Piezomodulated absorption spectra of Langmuir-Blodgett films of (C8H17)(8)H(2)Pc and (C12H25)(8)H(2)Pc were measured at 100 K. The separations of four absorption bands (1.60, 1.64, 1.76 and 2.05 eV) are increased by a uniaxial compressive stress applied along the film plane. These spectral features are explained by assuming lateral interactions among the pi electrons of the H(2)Pe rings which are parallel to the surface.