Several marine boundary layer (MBL) models have been developed over the last few years to predict the propagation behavior of electromagnetic radiation near the sea surface. Originally, they were developed to model the refractive effects of the MBL on radar systems, but in recent years they have been extended for use at visible and infrared wavelengths. Three of the more advanced models are DREV's L(W)WKD model (Canada), CELAR's PIRAM model (France) and the LKB model developed in the U.S. Only very limited comparative studies have been performed between them. This study discusses the differences between these models for a large number of realistic atmospheric conditions. In particular we present the differences between the calculated roughness heights, scaling constants, and vertical profiles with respect to various meteorological parameters.