The most usual measure against saltwater intrusion is the artificial recharge, which presupposes that sufficient amounts of fresh water or pretreated water are available (van Dam, 1999). An alternative measure, when such waters are not available, is the construction of cut-off walls near and longwise the coastline. Investigations on the effect of cut-off walls on saltwater intrusion have been presented by Luyun et al. (2008). The purpose of the present study is to provide criteria for the design of such structures which effectively act as countermeasures to saltwater intrusion. Confined, homogenous, isotropic and anisotropic coastal aquifers under no pumping conditions have been considered. The flow is assumed to be steady. The investigation is performed numerically using the SUTRA code (Voss & Provost, 2008). Both vertical cross sections and three dimensional configurations have been considered. The results show that the construction of cut-off walls is a promising technique against saltwater intrusion.