The mechanical properties of γ-TiAl based alloys are determined by their microstructure. The deformation characteristics of two-phase alloys, consisting of the γ-TiAl phase and a small volume fraction of the α2-Ti3Al phase, are simulated by a 3-dimensional micromechanical model based on the unit cell technique using the finite element method. This model considers crystallographic slip and deformation twinning as the deformation mechanisms in addition to the elastic behaviour. The crystallography and the microstructure are considered within the framework of crystal plasticity. Initially, this micromechanical concept was applied to polysynthetically twinned (PST) single crystals. The results of the simulation reflect the experimentally observed anisotropic plastic behaviour of the lamellar microstructure. It can be shown that the chosen micromechanical model reproduces the deformation mechanisms in a realistic way. Consequently, the concept has been extended to polycrystalline materials. In order to start with a rather simple case, a so-called near-γ microstructure is chosen. Furthermore, it is demonstrated that only a fully three-dimensional modelling allows reasonable predictions.