Heating of acrylonitrile, vinyl acetate and divinylbenzene porous copolymers (AN-VA-DVB) with aminoguanidine salts in alkaline medium leads to aminolysis and hydrolysis of the nitrile groups and hydrolysis of acetyl groups. As a result, an amphoteric chelating resin with guanidyl and carboxyl groups at a concentration of ca. 1 and 2-4 mmol/g, respectively, is obtained. The resin possesses a porous structure with a mean pore radius of 5.6 nm in swollen state. The sorption of Cu(II) ions increases with increasing content of functional groups, and reaches 120-170 mg/g at pH 5. The equilibrium sorption is attained after 300 min. The infrared (IR) spectra of resins confirm that both guanidyl and carboxyl groups form complexes with Cu(II) ions. From analysis of the sorption degree of Cu(II) ions it can be concluded that statistically two groups (carboxyl or/and guanidyl) participate in the complexation. Electron paramagnetic resonance (EPR) spectra of the resins suggest that at low pH the complexes of Cu(II) ions with carboxyl groups dominate. At the pH range 3-8 the formation of Cu(II) complexes with carboxyl and guanidyl groups is evident. At pH > 9 three or four nitrogen atoms participate in coordination sphere around Cu(II).