We assessed the diagnostic value of circulating VEGF as a tumor marker in patients with lung cancer and compared its clinical utility with that of other markers such as carcinoembryonic antigen (CEA) and cytokeratin 19 (CYFRA). One hundred and sixty non-small cell lung cancer patients and 70 healthy volunteers were included in the study. Circulating VEGF was assessed by enzyme-linked immunosorbent assay (ELISA). The serum concentrations of both CEA and CYFRA were measured by means of immunoradiometric assays. The diagnostic value of plasma VEGF (VEGFp) was better than that of CYFRA and similar to that of CEA. When the diagnostic value of VEGFp and CEA for the diagnosis of adenocarcinoma was compared, the two markers proved to have nearly equal discriminatory power. In diagnosing squamous cell carcinoma, VEGFp showed less discrimination than CYFRA. When the diagnostic value of VEGFp was analyzed for stage I adenocarcinoma patients, VEGFp was slightly more discriminatory than CEA. The combination assay of VEGFp and CEA had a sensitivity of 75% and a specificity of 60% at a cutoff of 104.4 pg/mL for VEGFp and 5.2 ng/mL for CEA. The combination of VEGF and CEA was superior to CEA alone in the early diagnosis of adenocarcinoma of the lung.