For the low-temperature separation of a gaseous mixture containing essentially hydrogen, C.sub.1+ -hydrocarbons, and carbon monoxide, resulting in a purified gaseous mixture to be processed, after the low-temperature separation, in methanol synthesis, the gaseous mixture is cooled and subsequently fed to a scrubbing column to scrub out the C.sub.1+ -hydrocarbons with liquid CO. A product containing essentially hydrogen and carbon monoxide is obtained at the head of the scrubbing column. The resultant liquid CO, loaded essentially with the C.sub.1+ -hydrocarbons, is withdrawn as the sump product from the column and introduced into a C.sub.1+ -CO separating column.