The chelation properties of the addition-type polymers poly(amidoxime-hydroxamic acid) and poly(N-methyl amidoxime-N-methyl hydroxamic acid) toward some trivalent lanthanide metal ions [La(III), Nd(III), Sm(III), Gd(III), and Tb(III)] were studied by a batch equilibration technique as a function of contact time, pH, and counterion. The effect of the crosslinker, divinylbenzene, was also studied. The selectivity and binding capacity of the resins toward various lanthanide metal ions are discussed. (c) 2005 Wiley Periodicals, Inc.