Molecular dipole polarizabilities of HHeF, HArF and HKrF were computed with the standard ab initio theoretical methods, SCF, MP2 and QCISD, using a 6-311 + +G(2d,2p) basis set. These results were compared with polarizabilities obtained from density functional theory (DFT) using the B3LYP, HCTH and VSXC functionals. It was found that, in contrast with a molecule like HF, the HRgF molecules (Rg = rare gas) have large average polarizabilities and polarizability anisotropies. Good agreement was found between the MP2 and QCISD methods, but (for HRgF) the corresponding SCF and DFT values are smaller in magnitude. (C) 2004 Published by Elsevier B.V.