The design of miniaturized planar and nanowire field effect devices for CMOS-compatible nano-electronics poses new challenges in the field of nanostructure modelling. Pros and cons of innovative devices incorporating different channel materials (Si, Ge, strained-Si, III-V) and crystal orientations need to be assessed. Transistors with body thickness (TSi) and channel length (L) of few nanometres have been demonstrated [Uch02,Wak03], where strong quantization effects in the vertical (y) direction coexist with quasi-ballistic, far from equilibrium carrier transport in the lateral (x) direction. In the field of engineering applications, full quantum–mechanical modelling of realistic nano-transistors has been so far mainly restricted to ballistic transport [Lau04]. However, scattering in the channel is still remarkably important to predict the drain current, even for nano-devices with L ≈10 nm [Pal04]. Moreover, it is unclear if the complex full quantum treatment of the scattering would lead to manageable numerical models, and if the expected huge computation times will be paid off by improved accuracy. In this contribution, we report recent advances in the development of an efficient modelling framework capable to combine the accuracy of quantum mechanical simulations with a semiclassical treatment of carrier transport aimed at the accurate calculation of the main performance metrics of planar (and wire-like) devices for nano-electronic applications.