Mesenchymal-epithelial transition factor (MET) plays a critical role in the development and progression of lung cancer. We aimed to quantify the level of serum MET DNA, analyze its diagnostic value, and provide a novel biomarker for lung cancer.Serum MET DNA was extracted from 95 patients with lung cancer, 10 with benign lung diseases, and 34 healthy volunteers. MET DNA was quantified using real-time fluorescent quantitative polymerase chain reaction (FQ-PCR). Data were analyzed using statistical software SPSS 17.0.Serum MET DNA level in the lung cancer group was higher than in the healthy group and benign lung diseases group. Serum MET DNA level was higher in lung cancers patients with smoking, squamous cell carcinoma, advanced TNM stage, and increased tumor size. The difference in serum MET DNA level was not related to sex, age, and lymph node metastasis among the lung cancer patients. The receiver operating characteristic curve showed a sensitivity of 72.6% and specificity of 90.9% for the ability of serum MET DNA to detect lung cancer at the cutoff value of 1.30 × 10(4) copies/μL. The association of serum MET DNA level with existing clinical lung tumor markers was analyzed, including neuron-specific enolase, squamous cell carcinoma antigen, and cytokeratin fragment 21-1. With the combination of serum MET DNA, the sensitivity was raised from 39.1%, 24.9%, 66.1% to 83.3%, 79.4% and 90.7%, respectively.Quantification of serum MET DNA by FQ-PCR may serve as a novel accessible diagnostic tool for the clinical screening and detection of lung cancer.