【Objective】To investigate the expression and the clinical significance of macrophage migration inhibitory factor （MIF）in the serum and lung tissues of the patients with non-small cell lung cancer（NSCLC）.【Methods】Eighty-eight eligible inpatients were confirmed by pathology of lung tissues，including 66 patients with NSCLC and 22 patients with benign lung lesions. ELISA was performed to measure serum concentration of MIF of these patients，which was compared with 30 healthy individuals. Meanwhile，immunohistochemistry（IHC）was performed to examine the expression of MIF in the lung tissues of the two groups. MIF expression level was compared between two groups and among different subgroups of NSCLC. The correlationship between serum MIF level and high expression rate in lung tissues was also analyzed. All the data were analyzed by SPSS17.0.【Results】The serum concentration of MIF in NSCLC group was significantly higher than that in healthy control（14.79 ng/mL vs 10.69 ng/mL，P=0.001）， and was slightly higher but not significantly different from benign lung lesions group（14.79 ng/mL vs 13.68 ng/mL，P=0.580）. The comparison among subgroups of NSCLC showed that the serum MIF level was not only correlated with the histological grade and clini? cal stage of the cancer，but also correlated with the gender and smoking history of the host. Immunohistochemistry showed that theMIF high expression rate in the lung tissues of NSCLC was markedly higher than that of benign lung lesions group（30.3% vs 4.5%， P=0.014）. Among the subgroups of NSCLC，IHC showed MIF high expression rate was correlated with the histopathologic types and clinical stage of the cancer. Simultaneously，the serum MIF level showed a positive correlation with MIF expression rate in the lung tissues in all patients and NSCLC group（P<0.05）.【Conclusion】MIF was strongly related to the clinicopathological characteristics of NSCLC. It could be helpful for the diagnosis and clinical evaluation of NSCLC.