The sorption capacity and selectivity of the chemically stable, macroporous phenol-formaldehyde resins with phenolic ion-exchange groups only, towards alkali metal ions have been studied. The selectivity of these resins towards rubidium and cesium ions were found to be significantly greater than that of the sulfonic, carboxylic, phosphonic, nitrated sulfonic and sulfonic-phenolic ion-exchange resins. The contributions of the ion-exchange and molecular sorption mechanisms to the sorption capacity and the selectivity were determined. The synergetic action of the phenolic active groups on the properties of ion-exchange resins is discussed. The resins with phenolic ion-exchange groups only were found to be very efficient for separation of the rare alkali metal ions.