Values of coefficients of crystalline packing density, Kc, calculated for a large number of polymers with chain backbones consisting of single carbon—carbon, carbon—oxygen, etc., bonds, exhibit strong dependence on polymer chain conformation in the crystalline state. It was established that Kc values tend to decrease regularly with the increase of chain “thickness” expressed by molecular cross-section, A, for polymers with helical conformation, while the reverse was true for extended-chain polymers. This difference is consistent with previously obtained results and can be derived analytically.