Isotropic hyperfine coupling constants of first-row atoms from B-F and the BH2 radical are calculated analytically from the coupled-cluster (CC) relaxed density with a variety of extended basis sets. We employ-both restricted and unrestricted Hartree-Fock reference functions, with the CC singles and doubles (CCSD), CCSD with noniterative triples [CCSD+T(CCSD) and CCSD(T)] methods. The latter provide excellent agreement with experiment. We also consider the role of orbital relaxation and atomic basis functions in accurate predictions.