In this paper, the influence of the hydrodynamic effects on the plug flow model deviation in the hydrodesulfuration (HDS) and hydrodemetalation (HDM) reactions of a petroleum residue is evaluated. The study has been carried out in a small pilot scale trickle bed reactor in continuos operation at 375 degreesC and 10 MPa of partial hydrogen pressure with a commercial NiMo/alumina catalyst. The nickel removal reaction, a first-order liquid-limited reaction, was used to test the predictions of several models, which incorporate the influence of the hydrodynamics on the catalyst utilization. For this task, additional experiments in a stirred tank reactor at the same conditions were done in order to determine the value of the effectiveness factor for denickelation reactions. Comparison of model predictions and experimental data indicates that the use of a hydrodynamic parameter in the models improves the data fit.