The surface-complexation theory was applied for the description of ion-exchange equilibria on nonconventional strong base anion exchangers with pyridine structures. Binary equilibria are described by a logarithm equilibrium parameter that is a linear function of the composition of the resin phase for chloride/nitrate, chloride/bicarbonate, and chloride/sulfate ion exchanges. Evaluation of date demonstrates that there are similar predictions from ion-exchange isotherms and the surface-complexation theory for the studied ion exchanges. We assume that ion-exchange equilibrium, regardless of its approach model, depends on the relationship between the chemical structure of the functional sites of the ion exchanger and the counterions that partake to the ion-exchange process.