Quantum corrections in the moderately low-temperature regime to the interaction potential energy of two permanent molecular dipoles are evaluated through the Wigner-Uhlenbeck-Gropper (WUG) semi-classical expansion of the density matrix, whose leading term is proportional to h(2), the dipoles being assumed in oscillatory motion around their position of minimum energy. Application of the resulting formulae to the ground states of a few heteropolar diatomic molecules and radicals shows that the quantum correction is not negligible, being particularly relevant for BH and OH. (C) 2010 Elsevier B.V. All rights reserved.