A herbicidal composition is here disclosed which exerts an excellent herbicidal activity and which is harmless to paddy rice.A 1-[1-methyl-1-(substituted phenyl)ethyl]-4,5-dimethyl-3-(substituted phenyl)-3-pyrroline-2-one derivative represented by the formula (I) ##STR1## (wherein X is a chlorine atom, fluorine atom or bromine atom; Y is a hydrogen atom, fluorine atom, chlorine atom or methoxy group; Z is a hydrogen atom, fluorine atom, bromine atom or chlorine atom; and Q is a hydrogen atom or fluorine atom)is a novel compound, and the herbicidal composition containing this compound as a herbicidally active ingredient has the strong activity and high selectivity as the herbicidal composition for paddy fields.