Volumetric mass-transfer coefficient in the gas phase, k(G)a, for Mellapak 250.X and 250.Y structured packings has been measured by standard method of absorption of SO2 from carrier gas to aqueous solution of NaOH in the i.d. 150.6 mm absorption column. Three carrier gases - He, N-2 and SF6 - have been utilized providing wide range of Sc-G from 0.49 to 2.32. The gas-phase mass-transfer coefficient, k(G), has been calculated from the experimental k(G)a data as the ratio of k(G)a and of the effective interfacial area, a, measured utilizing CO2/NaOH system. The experimental and literature k(G) data for Mellapak 250.X, 250.Y, 350.Y and 500.Y have been correlated by dimensionless correlation Sh(G) = 2.7 + 0.038 . Re-LG(0.88).Sc-G(beta) with beta = 0.33 + 0.9 . exp (-0.6 . Sc-G). The correlation fits the data in the wide range of Re-LG and Sc-G covering the process conditions of common absorption and distillation columns. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.