Dicarboximides of the general formula Ia and Ib ##STR1## where X is oxygen or sulfur, R.sup.1 is hydrogen, cycloalkyl, alkyl, hydroxyl, alkoxy, cyanoalkyl, alkenyl, alkynyl, phenyl, naphthyl or a 5-membered or 6-membered heterocyclic structure, where the stated radicals may be substituted, andR.sup.2 and R.sup.3 are each nitro, cyano, halogen, amino, mono- or dialkylamino, alkylcarbonylamino, unsubstituted or halogen-substituted alkoxy or alkylthio, alkylsulfonyl, haloalkylsulfonyl, alkenyl, alkynyl, phenyl, phenoxy or phenylthio or one of the radicals R.sup.1, with the proviso that specific compounds named in the description are excluded.Processes for the preparation of the compounds Ia and Ib and herbicides containing them.