The study focused on the use of associated and non-associated plasticity models in FEM simulations, with particular focus on the role of the dilatancy angle. The dilatancy angle was shown to significantly influence both the shear strength, the deformation behaviour of soils and the mesh dependence of model outcome, particularly in situations with confined or constrained deformation. To evaluate this, three cases were analyzed: Direct Simple Shear (DSS) test, slope stability, retaining structure.