Rare gas matrix effects on hyperfine coupling constants of N-2(+), BO, AlO and GaO were investigated by performing density functional calculations with 6-311 + G(3df) basis sets, using the polarizable continuum model with dielectric constants epsilon from 1 to 2. Known experimental values of A(ISO) (Al-27) for AlO correspond to e values of about 1.1 in Ne (766 MHz), 1.75 in Ar (899 MHz), and 1.85 in Kr matrices (920 MHz). A(iso)(M) of BO, AlO and GaO (MO) increases with epsilon, but A(dip)(M) and A(dip)(O) decrease, indicating that the s-spin density on M increases at the expense of p-spin densities on M and O. (c) 2005 Elsevier B.V. All rights reserved.