Abstract Slamming pressures provide one of the most important load sets for the design and classification of ships and offshore structures. These loads are highly localized and nonlinear, and therefore difficult to predict. Computational Fluid Dynamics (CFD) is a viable tool for their estimation, but validation must be demonstrated before its use is acceptable in standard practice. This paper addresses validation of slamming pressure predictions for two popular software packages: OpenFOAM and Star-CCM+. Both 2D and 3D tests are undertaken, and the predicted pressures compared to available validation-quality experimental data. The 2D cases involve tests of generic ship sections dropped from different heights. Three-dimensional simulations utilize a scale model 10K TEU container ship at different speeds operating over a range of incident wave conditions. The dynamic overset grid technique is applied to handle large-amplitude motions. Good agreement between CFD and experimental data is achieved in the bow area, along the bottom plating, and in the topsides flare area. A few of the comparisons (e.g. on the flat deck) highlight areas where additional work is justified. Overall, the results demonstrate the accuracy, flexibility and robustness of CFD performed using the overset grid technique.