We have used very large, purpose-oriented Gaussian-type basis sets to calculate static electric (hyper) polarizabilities for COS and NNO. For COS, we have obtained near-Hartree-Fock values with a [9s6p5d2f1g/ 9s6p5d2f1g/9s8p5d2f1g] basis set. Our best SCF values for the mean first and second hyperpolarizability of COS are (beta) over bar /e(3)a(0)(3)E(h)(-2) = -75.7 and (gamma) over bar /e(4)a(0)(4)E(h)(-3) = 4966. For NNO a [9s6p5d3f1g/9s6p5d3f1g/9s6p5d3f1g] basis yields SCF values (beta) over bar /e(3)a(0)(3)E(h)(-2) = 38.0 and (gamma) over bar /e(4)a(0)(4)E(h)(-3) = 1369. Electron correlation effects have been calculated at the CCSD(T) level of theory. Our best values for the respective corrections are (beta) over bar /e(3)a(0)(3)E(h)(-2) = -22.9 (COS), -2.2 (NNO) and (gamma) over bar /e(4)a(0)(4)E(h)(-3) = 1383 (COS), 485 (NNO) (C) 2010 Elsevier B. V. All rights reserved.