The paper presents the results of numerical calculations of the stability and deformation process of several idealized slopes performed by the elasto-plastic finite difference method, using the commercial codes FLAC3D and FLAC2D. The results of 3D analysis of these slopes are compared with those obtained by the 2D method. The behaviour of slopes of different shapes and inclinations was analyzed. The calculations were carried out for flat, concave and convex slopes inclined at 30°, 45° and 60°, taking into account the influence of the lateral constraints of the slope. Two variants of the medium were analysed, i.e. the mass with no friction and with no cohesion. A comparison of 3D calculation results with those obtained by the 2D limit equilibrium analysis indicates that the 3D approach produces almost always higher safety factors than does the 2D method.