Possible structural aspects are discussed that justify the different resistance to reduction of 2,3,5-triphenyl-2 H-tetrazolium chloride (TTC) both chemically (by reaction with ascorbic acid (ASC)) and electrochemically, in the presence of different polyelectrolytes such as poly(sodium 4-styrenesulfonate) (PSS), poly(sodium 4-styrenesulfonate- co-sodium maleate) at two different comonomer compositions (P(SS 1- co-MA 1) and P(SS 3- co-MA 1)), and poly(sodium acrylate- co-sodium maleate) (P(AA 1- co-MA 1)). Different dissociation constants are found for the complexes between TTC and the different polyelectrolytes by diafiltration (DF). Related to this, spectroscopical differences are also found by (1)H NMR and UV-vis spectroscopies. Dynamic light scattering (DLS) showed a higher tendency to undergo intermolecular aggregation for P(SS 1- co-MA 1) in the presence of TTC, a result that could be related with a higher tendency for TTC to form hydrophobic ion pairs as a consequence of single stacking with the benzene sulfonate groups (BS) of this polyelectrolyte. On the other hand, the lower tendency for PSS to undergo intermolecular aggregation could be attributable to a higher probability to form more hydrophilic adducts by means of double stacking with TTC.