Three zeolites from Armenia, Georgia and Greece were treated with dilute KOH and subsequently either reacted with HCl or heated at 700 °C. KOH treatment increased slightly specific surface area and microporosity due to dissolution of amorphous material. Acid treatment increases significantly both the specific surface area and microporosity and decreases the cation-exchange capacity due to partial dissolution of both Si-tetrahedra and free linkages, which yields secondary micropores and destroys specific exchange sites of the zeolites. Heating decreases both specific surface area and microporosity