To identify aberrantly hypermethylated DNA in lung cancer cells we established a genome-wide analysis for hypermethylation sites, namely Methyl DNA Isolation and Amplification (MeDIA) coupled-CpG microarray analysis. In the comprehensive methyaltion profiling analysis between human lung cancer, A549 cells and normal NHBE cells, we observed that several clusters of genes show a significant level of aberrancy in CpG island methylation pattern in cancer cells compared to normal cells. We further identified PCDHGA12 gene as a new marker of non-invasive diagnostics for lung cancer based on followings. 1) Transcription of PCDHGA12 gene is reactivated after treatment of A549 cells with demethylating agent. 2) Bisulfide clonal-sequencing reveals that CpG island of PCDHGA12 shows a distinctive differential methylation between two cell lines. 3) Pyrosequencing-based quantitative methylation assay for such region in tumor and non-tumorous tissues from lung cancer patients shows aberrant hypermethylation in 37 (92%) of the 40 tumor tissues. In clinical validation by pyrosequencingin induced-sputum of lung cancer patients (n=87) and healthy controls (n=51), we observed aberrant hypermethylation incident at significantly elevated level in samples derived from lung cancer patients. According to the optimal threshold calculated by ROC curve analysis, sensitivity and specificity of PCDHGA12 was 86.2% and 82.4%, respectively. PCDHGA12 methylation status could be a potential methylation biomarker alone or combined with others for the screen and the detection of relapse of lung cancer.