The present invention relates to the use of herbicidal substituted phenyl-pyridazine-diones and substituted phenyl-pyridazinone derivatives of formula (I), in combination with herbicidal pyrazolo-lactam-carboxamides of formula (II) to control undesirable plant growth, in controlling weeds, including broad-leaved and/or narrow-leaved, monocotyledonous and/or dicotyledonous weeds, in crops of useful plants.