Hyponatremia following acute or chronic central nervous system injury which is due to excessive Na+ loss in the urine without an increase in the body fluid, has been described as Cerebral Salt Wasting Syndrome (CSWS). This syndrome is often confused with dilutional hyponatremia secondary to inappropriate ADH secretion. Accurate diagnosis and management are mandatory for to improve the course of the disease. In this study a patient with CSW Syndrome is presented and the treatment and diagnosis of this syndrome are discussed in view of the literature.