The formation of complexes between the cationic polyelectrolyte poly[3,5-bis(dirnethylaminomethylene)hydroxystyrene] (Q-N-PHOS), bearing two cationic sites per repeating unit, and DNA molecules in aqueous solutions is investigated at pH 7 and at various salt (NaCl) concentrations and DNA/polymer ratios. The structural, characteristics of the polyplexes at different DNA/polymer ratios were characterized in terms of mass, size, and charge using, static, dynamic, and electrophoretic light scattering and fluorescence spectroscopy. The results indicate that the complexes have a loose spherical morphology with size in the range of 45-100 nm depending on polymer to DNA-ratio-and ionic strength-of the solution. Most interestingly, it is found that the polyplexes response to changes in the ionic strength of the surrounding solution after complexation depends strongly on the initial solution ionic strength during complex formation. This also points to differences in the nanostructures of polyplexes formed at different ionic strengths.