The atomization energy and structure of SO3 have been calculated using the advanced ab initio method, CCSD(T), in combination with the newly revised families of correlation consistent basis sets, cc-pV(n + d)Z and aug-cc-pV(n + d)Z (where n = D(2), T(3), Q(4), or 5). The impact of these sets upon structure and energy has been examined, as has convergence behavior toward the complete basis set (CBS) limit. Overall, these revised sets have a particularly strong effect upon energies determined using the lower level basis sets, and can reduce the unusually large deviation from experiment by over half. (C) 2004 Elsevier B.V. All rights reserved.