Influence of roll motion on the mass transfer performance in laboratory- and pilot-scale structured-packing columns was investigated. A six-degree-of-freedom motion parallel platform was adopted to mimic different sea states of roll motion, and the relative change in the mass-transfer area caused by roll motion was obtained using an air-NaOH system. The experimental results showed that both enhanced and deteriorative mass transfer phenomena could be induced by roll motion, which results from the combined effect involving the operating conditions, packing types and sea states. Based on these results, a nominal maximum rolling velocity was proposed. The nominal maximum rolling velocity was positively correlated with the relative change in the mass-transfer area. Furthermore, the results indicated that tilt could be regarded as an extreme sea state of roll motion. (C) 2017 Elsevier Ltd. All rights reserved.