A 56-year-old woman, with dysgeusia in which nearly all food was felt as sweet, was admitted to our hospital seeking for treatment. Serum sodium concentration was 113 mmol/L, but serum creatinine, zinc, urea nitrogen, and potassium, as well as blood glucose, were all within normal ranges. Dysgeusia disappeared when serum sodium level was normalized, but recurred when hyponatremia relapsed. She was diagnosed as having large cell lung carcinoma. We considered that the cause of hyponatremia was inappropriate secretion of antidiuretic hormone (SIADH) due to lung carcinoma. Miraculin is one of taste-modifying substances which fits the sweet receptor site and induces a strong sweet taste. We considered that taste-modifying substances same as miraclin are involved in the pathophysiology of this disease.