Molecular polarizability can be used to gain an insight into the origins of polychlorinated dibenzo-p-dioxins (PCDDs) specific binding to their receptor protein. In this work, the effects of the basis set on the polarizability values calculated at the HF level of benzene, chlorobenzene, and dibenzo-p-dioxin (DD) are analyzed. The geometry optimized with the 3-21G basis set and polarizability calculated with the 6-31G(sd,sp) basis set give reliable values useful for comparing polarizabilities of PCDDs with reduced computational costs. The study for two tetrachlorodibenzo-p-dioxin isomers highlights interesting differences in the molecular polarizability tensors as well as in the polarizabilities of C-Cl bonds related to the different chlorine positions on the aromatic skeleton.