In a process for discriminating cis- and trans-1,3-diaminocyclohexanes, a mixture of cis- and trans-1,3-diaminocyclohexanes is reacted with carbon dioxide or a reactive carbonic acid derivative and the urea of the cis-1,3-diaminocyclohexane, which can be separated off by means of a mechanical separation method, is obtained selectively. 4-Methylcyclohexane-1,3-diamine and/or 2-methylcyclohexane-1,3-diamine having a trans content of 99 mol % or more are obtainable in this way.