Theoretical investigations on the structure, energetics and vibrational spectra of sulfuric acid complexes with carbon dioxide have been performed at both the B3LYP/6-311++G(d,p) and correlation Moeller-Plesset MP2 level. The calculations showed that H2SO4-(CO2)(n) (n = 1, 2) complexes are formed by an end-on O=C=O... HO interaction, similarly to B3LYP/cc-pVDZ results obtained by Givan et al. [J. Mol. Struct. 604 (2002) 147]. The (H2SO4CO2)-C-... and H(2)SO(4)(...)2CO(2) species were found to be stable and the addition of a second CO2 group results in the growing strength of the interaction, reflected in the shifts for the OH stretching vibrations for the system. In addition. the potential energy distributions (PED) were calculated in order to obtain detailed vibrational assignments. (C) 2003 Elsevier Science B.V. All rights reserved.