Industrial fly ash was converted hydrothermally to a zeolite in aq. NaOH soln. at 70 degrees C and used for sorption of SO2 at 293 K optionally in presence of H2O vapour. Langmuir, Sips and Dubinin-Radushkevich (DR) equations were used for description of isotherms. The addn. of H2O resulted in increasing the sorption efficiency. The zeolite sorbent was regenerable. The best fit was found for the DR equation.