A simple scheme for the evaluation of the core spin-polarization contribution within pseudopotential electronic structure methods is proposed. The method uses a reconstruction of the all-electron wave functions and the frozen valence spin-d. approxn. to solve the Kohn-Sham equations for core electrons only. The core contribution to the spin-d. at the point of the nucleus corrects for the leading error in the Fermi contact hyperfine coupling consts. within pseudopotential-based electronic structure calcns. The correction is implemented in the framework of pseudopotential plane-wave d. functional theory. Comparison with all-electron STO calcns. on a no. of mol. radicals contg. first-row elements proves the accuracy of this approach. [on SciFinder (R)]