The paper compares two different imaging techniques for the investigation of the hydrodynamics in a laboratory packed bed reactor operating at different stationary states and with two different particle packings. The wire-mesh sensor offers cross-sectional liquid holdup distribution imaging at an ultra high speed of 10000 frames/s and good spatial resolution of 6 mm. It is therefore a very useful imaging tool for transient and periodic flow conditions. Up to now its influence on the flow in a packed bed was never analyzed. γ-ray computed tomography uses 662 keV γ photons to obtain cross-sectional phase distribution images. It offers as well a good spatial resolution of 2 mm and does not influence the flow but needs rather long scanning times. As a noninvasive technique γ-ray tomography has been used as a reference modality to evaluate the wire-mesh sensor measurements. Data from both imaging modalities are compared utilizing different analyzing models and showed good agreement. For the wire-mesh sensor only marginal intrusive effects for the specific situation were found.