Two investigated antiferroelectric liquid crystals, MHPB(H)PBC and MHPB(F)PBC. were synthesized [1] and some their physical properties were described earlier [2]. Apart of the above, MHPB(H)PBC and MHPB(F)PBC have been studied by means of dielectric, densitometric, refractometric and X-ray measurements. Spontaneous polarization P-S and tilt angle theta in ferro- (SmC*) and antiferroelectric (SMCA*) phases of MHPB(H)PBC and MHPB(F)PBC have also been investigated. Transverse oct and longitudinal al molecular polarizabilities have been calculated front the ordinary n(o) and extraordinary n(e) refractive indices and density rho of MHPB(H)PBC and MHPB(F)PBC, using Neugebauer's, Vuks and Lorentz equations with both Haller and Subramhanyama extrapolation procedures. Effective values of the molecular dipole moment p have been calculated from electric permittivity E in the 1 phases of these compounds, using Maier and Meier equation.