1-Arylimidazol-2(1H)-ones are shown to be readily lithiated, using 2 mol equiv. of n-butyllithium, on the benzene ring, ortho to the heterocycle. 1-Aryl-4,5-dihydroimidazol-2(1H)-ones also undergo metalation on the aromatic substitutuent ortho to the heterocycle, but less efficiently. 1-Aryl-3-methylimidazol-2(1H)-ones are lithiated on the heterocyclic ring and then on the benzene ring ortho to the heterocycle. No ortho-directing effect was found for 1-aryl-4,5-dihydro-3-methylimidazol-2(1H)-ones.Key words: ortho-lithation, ureas for directed ortho metalation, 1-arylimidazol-2-ones, 1-arylimidazolidin-2-ones.