Ultrafast X-ray tomography and wire-mesh sensor as two high-speed imaging modalities were applied to study upward gas–liquid flow in a vertical pipe of 50mm inner diameter. High speed scanning of the flow cross-section was performed with 2500 frames per second with both modalities. Sequences of two-dimensional distributions of local gas fraction were acquired and further analyzed. Radial profiles of time averaged gas fraction distributions show a good agreement for both the imaging techniques. Furthermore, radial gas velocity profiles were obtained from a temporal cross-correlation of the image data of both measurement techniques and also bubble size distributions from binarized image data were compared.