This paper reports the serum selenium concentration in 100 cases of lung cancer patients and 100 healthy controls. The results showed that the serum selenium level in patients with lung cancer was significantly lower than that of controls. Serum selenium level in lung cancer patients was inversely related to the stage of cancer, the amount of tobacco abuse and the serum Cu level. It was positively correlated with patient's nutritional status and the serum albumin level. Serum selenium level was decreased with cancer progression and increased with disease remission. These results suggest that the lower serum selenium level in lung cancer patients was the result rather than the cause of cancer.