Objective:To investigate the significance of detecting plasm sCD74 in differential diagnosis of lung cancer and benign pulmonary diseases. Methods:Plasm samples were collected after centrifugation of EDTA blood specimens from patients of lung cancer and benign pulmonary diseases. The plasm level of sCD74 was identified and quantified by ELISA. Results:The concentrations of sCD74 in patients with lung squamous carcinoma,adenocarcnoma and control subjects were(2.51 ± 1.36)ng/ml,(2.14 ± 1.16)ng/ml and(1.91 ± 0.78)ng/ml. The concentrations of sCD74 in patients with lung adenocarci-noma were higher than those in the other two groups,but only significantly higher than that in control subjects(P < 0.05). Conclusion:Detecting of plasma sCD74 may play a role in diagnosis of lung adenocarcinoma.