The present invention relates to a process for preparing sulfur-containing compounds of the general formula I ##STR00001## in which Q, R.sup.1 and R.sup.2 are each independently defined as follows: Q: --S-- or --S--S--, R.sup.1: hydrogen or saturated or unsaturated, linear or branched C.sub.1-C.sub.30-alkyl radical, R.sup.2: hydrogen or saturated or unsaturated, linear or branched C.sub.1-C.sub.30-alkyl radical, where R.sup.1 and R.sup.2 are not simultaneously hydrogen, by reacting a mixed gas stream comprising hydrogen sulfide, with or without oxygen, with linear or branched C.sub.1-C.sub.30-olefins, which comprises carrying out the reaction in the presence of water and carbon dioxide at a pressure of from 2 to 325 bar.