Density functional theory (DFT) methods have been applied to the study of the interactions between sulfur dioxide and oxygen- and nitrogen- containing compounds in the gas and solution phases. The complexes studied were SO₂-NH₃, SO₂-NH₂CH₃, SO₂-NH(CH₃)₂, SO₂-N(CH₃)₃, SO₂-H₂O, SO₂-CH₃OH, and SO₂-O(CH₃)₂. The level of theory used was B3LYP and the basis sets employed included 6-31+G(d), 6-311++G(d,p), and 6-311++G(2df,2pd). The gas phase and solution phase complexes exhibit significant differences in terms of geometry, energies, and other properties. Some examples of this are demonstrated in the dipole moment, for which the solution phase dipole moment was significantly larger than the gas phase dipole moment; on average the dipole moment difference ranged from 1.3 Debye for O-containing compounds to 3.5 Debye for N-containing compounds. Other trends were also observed for the S-N and S-O bond lengths. The S-N and S-O bond lengths for the solution phase were much shorter than the gas phase distances; on average the distances differed by 0.17 Å for S-O bond lengths and 0.33 Å for S-N bond lengths. The binding energies of these compounds also exhibited trends; on average the gas vs. solution phase binding energy difference ranged from 1.4 kcal/mol for O-containing compounds to 4.8 kcal/mol for N-containing compounds. The bonding in the complexes also was studied in more detail using Natural Resonance Theory (NRT) analysis.