We have developed analytical, models for the threshold voltage, the subthreshold swing and DIBL of undoped cylindrical Gate All Around (GAA) MOSFETs and Double Gate (DG) MOSFET using an analytical solution of the two-dimensional (2D) Poisson equation in which the mobile charge term has been considered. Using this new model, we have studied the scalability limits of GAA and DG MOSFETs and compared their performances. We have found that, to obtain a given performance, GAA MOSFETs can have a 33% shorter channel length than DG MOSFETs. (C) 2007 Elsevier Ltd. All rights reserved.