Two different series of smectic liquid-crystalline biphenyl carboxylates have been prepared and their smectic properties investigated. The 'lateral' alkyl chain at the branching carbon was varied from methyl to hexyl for the homologous series of 4-(1-alkylheptyloxycarbonyl)phenyl 4′-octyloxybiphenyl-4-carboxylates. The antiferroelectric phase (SCA(*)) was observed for the homologous series except the pentyl homologue. The smectic layer thicknesses for the series were found to increase as ascending the 'lateral' alkyl chain, indicating that the 'lateral' alkyl group of the series is in fact along the molecular long axis to some extent, which can occur if the molecule has the 'bent-shaped' structure.