This study was conducted to determine the SNP309 of MDM2 gene in lung cancer patients by PCR - RFLP (Restriction fragment length polymorphism - PCR) method. Ninety-eight patients diagnosed with lung cancer at the Respiratory Center, Nuclear Medicine and Oncology Center Bachmai hospital were selected to study the clinical features, histology and analyzed for MDM2 SNP309. The results showed that MDM2 - SNP309 with TG transition was identified, in which the genotype SNP309 TIG represented 48 percent, the TIT represented 26,5 percent and the GIG, 25,5 percent.