-This comparative study of mesozooplankton communities in the Tangier (Atlantic) and M'Diq (Mediterranean) regions was carried out in March, May and December 2006 and in May, July and November 2007. In both sectors, the zooplankton is mainly dominated by copepods, which represent 93% in Tangier and 87% in M'Diq, with respectively 85 species in 24 families and 81 divided into 22 families. Spatio-temporal analysis of Copepod specific richness data revealed highest values occurring in both areas during December 2006 and November 2007 with 36 and 30 species respectively. During other seasons, specific richness did not generally exceed 25 species. However, irrespective of area, the composition of the Copepoda population was usually dominated by Paracalanus parvus and Oncaea venusta. In terms of total density, the Atlantic is greater than the Mediterranean sector with a maximum density of 1093 ind.m −3 and 796 ind.m −3 , respectively, recorded in July and May, 2007. The Shannon diversity index was calculated and indicated that the Copepod community is more stable and balanced in the Tangier region compared to the M'Diq area, and in 2007 compared to 2006. Moreover, seasonal variation is more marked in the Atlantic than in the Mediterranean area and in both sectors, the autumn season is characterized by a low productivity but high specific diversity. Key words