Aim: The aim of this study was to investigate the polymorphism frequency of plasminogen activator inhibitor-1 (PAI-1) (rs1799889) 4G/5G in patients with lung cancer. Methods: In this study, 286 genomic DNAs (154 lung cancer patients + 132 subjects without lung cancer) were analyzed. Polymorphisms were determined by using the polymerase chain reaction (PCR) method, with 4G and 5G allele-specific primers. PCR products were assessed by a charge-coupled device camera and exposed to 2% agarose gel electrophoresis. Results: The frequencies of the PAI-1 gene 4G/5G genotypes were found to be 21% 4G/4G, 16% 4G/5G, and 62% 5G/5G in the control group and 31.4% 4G/4G, 30.8% 4G/5G, and 37.8% 5G/5G in the patient group. It was determined that the 5G/5G genotype frequency was high in patients in comparison with other genotypes. Conclusions: This study found a statistically significant difference between the groups with respect to genotype distribution. Consequently, we can say that the PAI-1 gene 4G/5G polymorphism is associated with lung cancer in Turkey.