The distributions of the mass transfer coefficient in horizontal 90 deg bends were measured under a range of two phase annular flow conditions. A dissolving wall technique at a high Schmidt number (Sc = 1280) is used for the measurements. The maximum mass transfer occurred on the centerline of the bend outer wall at an angle of approximately 50 deg from the bend inlet under all tested conditions. The area of maximum mass transfer rate was found to span approximately 30 deg in the circumferential direction. A second region of enhanced mass transfer occurred on the latter part of the bend with a local maximum occurring slightly off the bend centerline in some cases. Changing the air and water superficial velocities (Jv = 22–30 m/s, JL = 0.17–0.41 m/s) showed that the air velocity had a larger effect on the mass transfer rates than the water velocity; however, the effect of the water velocity on the mass transfer was not insignificant.