X-ray computed tomography (CT) was utilized to determine the effective wetted area and local liquid holdup for an air-water contactor containing structured packing. The experimental wetted area results were in agreement with results obtained from a traditional chemical absorption technique. The holdup varied significantly with vertical position. Areas near the joint region between adjacent packing elements exhibited holdup values greatly exceeding the values for holdup observed in the middle of the packing element. These findings will dramatically impact both design and model development for mass transfer devices containing structured packing.