Finding the cancer cells in pleural fluid of patients with lung can-cer by conventional cytology is always a difficult point. In order to enhance the diagnostic rate of pleural fluid with lung cancer, carcinoembryonic antigen (CEA) and cancer antigen 153 (CA153) were detected in serum and pleural fluid, and their diagnostic values on lung cancer were analyzed.Quantities of CEA and CA153 were detected by chemiluminescence in both serum and pleural fluid of patients with lung cancer (74 cases) and without lung cancer (34 cases).The levels of CEA and CA153 in pleural fluid of patients with lung cancer were significantly higher than those without lung cancer (P < 0.01). The levels of CEA and CA153 in serum of patients with lung cancer were distinctly higher than those without lung cancer (P < 0.01). The levels of CEA and CA153 in pleural fluid were obviously higher than those in serum (P < 0.01). The optimal diagnostic assay of lung cancer was CEA+CA153 combination: sensitivity and specificity were 85.1% and 97.1% respectively.It could be of important clinical significance for diagnosing lung cancer by assaying CEA and CA153 in pleural fluid of patients with lung cancer.