The flow pattern in a trickle-bed reactor (TBR) filled with structured packings (SPs) is inspected within a wide range of gas and liquid velocities using air and water, or CMC solutions of different viscosities, as model fluids. Flow regime transitions are identified from the analysis of time series of the current intensity measured with a polarized electrode that is part of the packing. Results are compared with a reported general correlation for determining flow regime transitions in conventional TBR.