The object of the analysis of the study is the hydrodynamics of a trickle bed reactor operating in both the gas continuous flow (GCF) and pulsing flow (PF) regimes. For the gas continuous flow regime the model developed by Grosser et al. [15] was subjected to a critical analysis. It was stated that the model derived for a uniform steady state has to be applied for design calculations. A simple phenomenological model of the propagation of a wave of liquid through the bed was suggested for the pulsing flow regime and verified on the basis of our own experimental data.