Cerebral salt wasting syndrome (CSWS) is a group of diseases that causes hyponatremia and dehydration following conditions including head trauma and subarachnoid hemorrhage. We experienced three cases with different chief complaints and consultation processes. An 86-year-old woman (Case 1) and an 83-year-old man (Case 2) were consulted for consciousness disturbance and hydrocephalus. Both cases had hyponatremia, hypouricemia, and obstructive hydrocephalus after trauma. A 51-year-old woman (Case 3) visited with dizziness and nausea. She had hyponatremia and hypouricemia after trauma. We diagnosed them with CSWS because of trauma history and examination findings. Although the mechanism of CSWS is unknown, it is pointed out to be related to suppression of reabsorption of sodium, uric acid and water in the proximal renal tubule by the natriuretic peptide. In cases with hyponatremia which progresses after head injury, we need to verify if hypouricemia is present so that CSWS is to be diagnosed, and if so, hyponatremia and dehydration should be corrected.