Plate fin-and-tube heat exchangers are widely used in several areas such as heating, ventilating, air conditioning and refrigeration systems. Nonuniformity of the inlet air flow in heat exchangers is first order importance and has decisive influence on their efficiency because it can intensify longitudinal wall heat conduction and the maldistribution of interior temperature. This study presents the results of three-dimensional (3D) Computational Fluid Dynamics (CFD) simulations aim to investigate the effect of inlet air flow maldistribution on the thermo-hydraulic performance of heat exchangers. Validation of the computation results with experimental data found in the literature has shown a very good agreement. Different computation test cases with a variety of inlet air flow distributions on in-line and staggered plate-fin-and-tube heat exchangers were run to systematically analyse their effects on system performance. The CFD results confirmed the importance of the influence of inlet fluid flow nonuniformity on heat exchanger efficiency. Results indicate that up to 50% improvement or deterioration in the Colbum j-factor are found compared to the baseline case of a heat exchanger with a uniform inlet air velocity profile. Moreover, the present investigation with respect to inlet flow maldistribution demonstrates that 3D CFD simulation is a useful tool for analysing, designing and optimising heat exchangers. Finally, the results of this study can be also of significant value for the optimum design of header and distributor configurations of heat exchangers to minimise maldistribution. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.