A two-zone two-fluid one-dimensional model was developed for the prediction of the irrigated two-phase pressure drop and the total liquid holdup in gas-liquid countercurrent columns containing structured packings and operated in the pre-loading zone. The model is based on the volume-average mass and momentum balance equations and the double slit model approximation. The model parameters, i.e., the two b2ed Ergun constants, were estimated using gas flow three-dimensional computational fluid dynamics (CFD) within representative elementary units coupled with a combined mesoscale-microscale predictive approach to apprehend the aerodynamic phenomena occurring at the macroscale in structured-packing-containing columns. The two-fluid model proved powerful in the prediction of the column hydraulics under various operational conditions such as atmospheric scrubbing or high-pressure/temperature distillation conditions for the Flexipac, Mellapak, Gempak and Montz packings. The satisfactory results obtained highlighted the breadth of applicability of the proposed approach especially for new designs or for optimal rating of existing equipments. The model can also prove powerful in the simulation and design of new geometries for structured packings. (C) 2003 Elsevier Ltd. All rights reserved.