The MM5 mesoscale meteorological model was run over the east Mediterranean focussing on the north part of Israel. Three days during June 1995 were simulated using two different parameterizations for the planetary boundary layer (PBL) available in the model: MRF and Blackadar. The variation of the atmospheric PBL was studied as a function of the distance from the coast and the effect of topography and sea breeze on it were examined. The following variables were analyzed: 1. PBL height, 2. Temperature profiles, 3. Water vapor mixing ratio, 4. Wind field, 5. Ground temperature. The diurnal variation of the PBL height was of the order of 2 km above the land and of the order of 400 m in the coast area. Maximum PBL heights above the land were obtained in the early afternoon while minimum PBL heights were obtained in the early morning. We discuss the effect of the PBL parameterizations on the model results. Among the differences between both parameterizations we emphasis the difference in the PBL height for unstable conditions.