A comparison was made between two-dimensional (2-D) and three-dimensional (3-D) finite element modelling for the prediction of welding deformation, giving consideration to the data available from each model versus the computational cost. The cases considered were butt welds in INCO 600 sheet (200 x 50 x 2 mm) made by TIG (triangular penetration) and energy beam (EB or laser) giving a parallel-sided joint, each under three conditions of restraint. Computational principles of the models are described and predicted evolution of deformation during welding and cooling is illustrated. Applicability of the two models is then discussed.