Physicochemical properties of polyelectrolyte poly(diallyldimethylammonium chloride) (poly(DADMAC)) and the copolymer of DADMAC with zwitterionic monomer 2-(diallyl(methyl)ammonio) acetate (DAMA) containing equimolar amounts of DADMAC and DAMA units were studied in aqueous solutions in the presence of ions of different sizes (Cl, Br, and I). The solutions were investigated by viscometry, analytical ultracentrifugation (AUC), nuclear magnetic resonance (NMR), dynamic (DLS) and static (SLS) light scattering. It was shown that an increase in the halogen ion size facilitated condensation of bulky anions on the polyelectrolyte chain. Ultimately, this resulted in deterioration of the solvent quality and collapse of the poly(DADMAC) coil in aqueous solution in the presence of iodine ions. Introducing DAMA units into the polymer chain exerted a positive effect on solubility of the resulting copolymer (poly(DADMAC-co-DAMA)) in aqueous solutions containing iodine ions.