A Monte Carlo investigation of quasi‐ballistic transport in scaled MOSFETs is presented. Taking into account a realistic velocity and electric field profile in ultra‐scaled transistors, the carrier mobility is calculated, observing a degradation of this macroscopic parameter strongly related to the peculiarities of the electrostatic profiles found for extremely short gate lengths. Simultaneously, the onset of ballistic phenomena within the channel is detected. A detailed investigation of the movement of carriers inside the channel allows providing numerous microscopic quantities related to electronic transport, such as mean free paths, transit times or average number of scattering mechanisms. Results evidence the existence of a significant proportion of ballistic carriers as the gate length is scaled down to few tens of nanometre. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)