The influence of LaCl , CeCl , and NdCl on the antioxidative defense system in maize seedlings under cold stress was investigated. It was found that maize seedlings cultivated in cold stress developed distinct cold symptoms, and the plant growth was significantly inhibited as expected, while Ln-treated seedling growth was improved. Cold stress in maize seedlings also increased the permeability of plasma membrane, malondialdehyde as a degradation product of lipid peroxidation, and reactive oxygen species such as superoxide radicals and hydrogen peroxide, and decreased activities of the antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, and glutathione content; however, Ln treatments cultivated in cold stress decreased the permeability of plasma membrane, malondialdehyde, and reactive oxygen species, and increased activities of the antioxidative defense system. It implied that Ln could increase oxidative-stress resistance under cold stress. On the other hand, the assay of physiological and biochemical parameters demonstrated that Ce relieving chilling injury of maize seedlings caused by cold stress was most significant, medium in the Nd treatment, and last in the La treatment. These results suggested that the increase of cold resistance of maize seedlings caused by Ln might be closely related to its properties of 4f electron shell and variable valence. © Springer Science+Business Media, LLC 2010.