BACKGROUND: Early detection and diagnosis is urgent for the sake of effective treatment strategy for lung cancer. However, a convenient, economical and relatively precise method is not available. We here report a prospective study to find the possible value of the combined use of four popular tumor markers in the early diagnosis of lung cancer among patients with suspicious nodules in the lung. METHODS: Six hundred and sixty inpatients with suspicious nodules in the lung were divided into a lung cancer group and a benign pulmonary tumor group according to post-operative histological examinations. Serum levels of four tumor markers including squamous cell carcinoma antigen (SCC), carcinoembryonic antigen (CEA), Cyfra 21-1 and neuron specific enolase (NSE) were assayed for each patient. Receiver operating characteristic (ROC) curves were constructed for each tumor marker. The power of lung cancer diagnosis of each tumor marker, as well as a combination of them were analyzed and compared. RESULTS: The serum levels (median, range) of SCC, CEA, Cyfra 21-1 and NSE were 0.44 (0.01 - 35.70) ng/ml, 2.49 (0.30 - 26.78) ng/ml, 2.30 (0.82 - 73.33) ng/ml and 10.54 (0.10 - 56.41) ng/ml respectively in lung cancer group, and were 0.32 (0.01 - 0.90) ng/ml, 1.60 (0.20 - 8.93) ng/ml, 1.41 (0.72 - 4.82) ng/ml and 9.36 (6.56 - 24.24) ng/ml respectively in the benign pulmonary tumor group. The difference in each tumor marker between the two groups was significant (P < 0.05). The ROCs of SCC, CEA, Cyfra 21-1 and NSE were 0.702 (95%CI, 0.654 - 0.751), 0.611 (95%CI, 0.563 - 0.659), 0.650 (95%CI, 0.601 - 0.700) and 0.598 (95%CI, 0.542 - 0.654) respectively, indicating very low power of these four tumor markers. When a combination of SCC, CEA, Cyfra 21-1 and NSE were employed, the diagnosis power was strengthened. CONCLUSION: SCC, CEA, Cyfra 21-1 and NSE are valuable in the early diagnosis of lung cancer among suspicious nodules in the lung, especially when they were assayed together for one patient.