Magnetic coupling constants J for the complete structures of heterobinuclear compounds GdCu(OTf)(3)(bdmap)(2)-(H2O). THF (1, (GdCuII)-Cu-III), [Gd(C4H7ON)(4)(H2O)(3)][Fe(CN)(6)]. 2H(2)O (2, (GdFeIII)-Fe-III), and [Gd(C4H7ON)(4)(H2O)(3)]-[Cr(CN)(6)]. 2H(2)O (3, (GdCrIII)-Cr-III) have been calculated by the combination of the broken-symmetry approach with the spin project method under the DFT framework. The calculated J values (3.6 (1), 8.1 (2), and 20.3 cm(-1) (3)) conform well to that of experimental findings (2.9(2) (1), 0.74(3) (2), and 0.40(2) cm(-1) (3)) with a small difference in absolute value. The compounds 1-3, whose J values are all positive, show ferromagnetic couplings between two metal centers; thus, their ground states are all in high-spin states. The spin density distributions are discussed in detail on the basis of Mulliken population analysis, taking into account the coexistence of spin delocalization and spin polarization mechanisms. For 1, the spin distribution in the ground state may be understood as a result of the competition between two mechanisms: a spin delocalization from Cu(II) and a spin polarization of Gd-III, and the former is dominant. In the cases of 2 and 3, both transition metal (Fe-III or Cr-III) and rare earth Gd-III display a spin polarization effect on the surrounding atoms, where a counteraction of the opposite polarization effects leads a low spin density on the bridging ligand C1N1. In the ground state of 3, the stronger polarization effect of Cr(III) even causes the positive spin density on the adjacent bridging atom N1, different from the situation in 2.