Abstract: Objective To investigate the clinical significance of fractional exhaled nitric oxide in lung cancer patients. Methods Clinical data, exhaled nitric oxide (eNO) measurements and pulmonary function test results of 164 patients with lung cancer by pathological diagnosis in our hospital from December 2012 to December 2014 were retrospectively analyzed. Another 172 healthy people were served as control group. Results The average exhaled nitric oxide level of patients with lung cancer was 33.85 ppb, while it was 16.80 ppb in normal control group, which showed significant differences (P＜0.05). In the lung cancer group, patients with FEV₁%≥80% had lower average exhaled nitric oxide level than patients with FEV₁%＜80% with significant differences (32.50 ppb vs 43.54 ppb, P＜0.05). Of the 164 cases, squamous cell carcinoma, adenocarcinoma, small-cell lung cancer, lung carcinoid tumor, and others accounted for 18.90%, 68.90%, 3.66%, 6.71% and 1.83%, respectively. The eNO levels in squamous cell carcinoma group, adenocarcinoma group, small-cell lung cancer group and lung carcinoid tumor group were 39.85 ppb, 32.94 ppb, 38.95 ppb, 24.48 ppb, respectively, which showed significant differences (P＜0.01). Conclusion The eNO levels in patients with lung cancer are higher than the normal level, especially in patients with squamous cell carcinoma and small-cell lung cancer. The measurement of eNO will be helpful in the diagnosis and classification of lung cancer.