Abstract Dimethyl sulfite has three conformers of low energy, GG, GT and GG′, which have significant populations in the gas phase at room temperature. According to theoretical predictions, the GT and GG′ conformers are higher in energy than the GG conformer by 0.83 and 1.18 kJ mol−1, respectively, while the barriers associated with the GG′→GT and GT→GG isomerizations are 1.90 and 9.64 kJ mol−1, respectively. Experimental data obtained for the compound isolated in solid argon, krypton and xenon demonstrated that the GG′→GT energy barrier is low enough to allow an extensive conversion of the GG′ form into the GT conformer during deposition of the matrices, the extent of the conversion increasing along the series Ar