The crosslinked resins poly(acrylic acid) (PAA) and poly[N-3-(dimethylamino)propyl acrylamide-coacrylic acid] [P(NDAPA-co-AA)] are obtained by radical polymerization and characterized by FTIR spectroscopy. PAA at basic pH exists basically as an acrylate anion that may contain end carboxylate groups or form bridges acting as mono- or bidentate ligands. P(NDAPA-co-AA) presents three potential ligand groups in its structure: carboxylic acid, amide, and amine. The trace metal ion retention properties of these two resins is compared by using the batch equilibrium procedure. The metal ions are contained in saline aqueous solutions and are found in natural seawater. The retention Of Cu(II), Pb(II), Cd(II) and Ni(II) metal ions is studied under competitive and noncompetitive conditions. The effects on the pH, contact time, amount of adsorbent, temperature, and salinity are investigated. The PAA resin presents a high affinity (> 80%) for Cu(IT) and Cd(II) ions. The P(NDAPA-co-AA) resin shows a high affinity for Pb(II) and Cd(II) ions. With 4M HNO3 it is possible to completely recover the PAA resin charged with Cu(IT) ions and the P(NDAPA-co-AA) resin charged with Pb(II) ions. The two resins show a high affinity for Cd(II) ions from the seawater containing Cu(II) and Cd(II) ions. (c) 2005 Wiley Periodicals, Inc.