Fluidised-bed catalytic cracking (FCC) is one of the most important processes in petroleum refining. FCC reactions occur in transported bed reactors, known as risers, exhibiting residence times between 2 and 4 s. Although the economical importance of catalytic cracking, simulation of operating conditions is rather empirical due to the complex interactions among operating variables. In order to improve simulation techniques, FCC processes should be modelled as much accurately as possible. In this work, a one-dimensional model that considers plug-flow of solid and gaseous phases is analysed. Two different approaches are considered, in the first one, the model consists only of mass and energy balances; in the second one, momentum balance is included to consider the axial pressure profile. Prediction of yield to products and conversion improves when the pressure gradient is modelled. This simplified description of hydrodynamics shows that more complete modelling of the hydrodynamics of the system improves the prediction of the behaviour of FCC risers, however this approach has not exhibited continuity in the FCC modelling literature. (C) 2004 Elsevier B.V. All rights reserved.