CCSD(T) calculations with triple-zeta valence plus polarization basis sets have been performed on HOSO and HSO2 to determine structures, vibrational frequencies, and infrared intensities for the first time with coupled-cluster methods. It is found that the planarity of HOSO is very sensitive to basis set. The calculated frequencies and intensities offer further support for the identification of HOSO and HSO, in rare gas matrices. (c) 2006 Elsevier B.V. All rights reserved.