Bubble columns are the reactors of choice for conversion of synthesis gas to liquid fuels (F-T synthesis). The F-T synthesis is an exothermic reaction and cooling internals are installed in the bubble columns to remove the heat generated in the reaction. The presence of the internals affects both the gas and liquid flow patterns in bubble column. This change is expected to reflect on the volumetric mass transfer coefficient. In this work, the impact of vertical cooling internals on overall gas hold-up and volumetric mass transfer coefficients is evaluated on 45 cm diameter pilot scale bubble column and 19 cm diameter lab scale bubble column. It was found that in presence of internals the gas hold-up in both the columns was increased, however no significant impact of presence of internals on volumetric mass transfer coefficient was observed. The gas hold-up and volumetric mass transfer coefficients evaluated in this work are compared with prediction from existing correlations. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.