Using the gel synthesis approach of polymer-analogous transformations, N-sulfoethylation of polyethylenimine was carried out by treating the polymer with sodium vinyl sulfonate. The compositions and structures of the products were characterized by elemental analysis, FT-IR spectroscopy, and 1H NMR spectroscopy. At pH 3.0-4.5 sulfoethylated polyethylenimine can selectively extract AgI and CuII from an ammonia-acetate buffer solution in the presence of a series of transition and alkaline-earth metals. At pH > 6.5 the sorbent can be used for the group extraction of a number of transition metal ions. The structural feature of the obtained derivative eliminates the selectivity of sorption of AgI ions compared to CuII ions, which has previously been revealed for the sulfoethylated derivatives of chitosan and polyaminostyrene.