In this paper we develop a compact model for ballistic/quasi-ballistic transport in Nanowire. Starting from the well-known approach of Natori/Lundstrom, we enhanced it by including an original modeling of SCE/DIBL (Short Channel Effect and Drain Barrier Lowering), scattering mechanisms and quantum mechanical confinement. Our drain current model has been validated by comparisons with numerical simulations at device and circuit levels. Finally, we used our model to simulate simple circuit elements and to evaluate the impact of Nanowire architecture on the device and circuit performances.