Chronic obstructive pulmonary disease (COPD) and lung cancer (LC) are a major cause of morbidity and mortality worldwide. In both diseases airways inflammation plays an important role. Functional promoter polymorphism, at the position -308, of tumor necrosis factor (TNF)-alpha represents attractive potential susceptibilty marker for both diseases. In order to investigate the role of this polymorphism in COPD and LC, a case-control study was performed. The patient groups consisted of 97 subjects with COPD and 70 subjects with LC, while the control group encompassed 102 subjects. Results of our study showed significant decrease of heterozygote for TNF-alpha-308 1/2 gene variant in COPD group in comparison to controls (p=0.043). According to our results heterozygous carriers of TNF-alpha-308 1/2 polymorphism had a2.3-fold decreased risk for COPD development (OR=0.44, 95%CI=0.20-0.97). In patients with lung cancer we also observed a trend of decreased distribution of TNF-alpha-308 1/2 heterozygotes, but statistical significance was not achieved. To our knowledge, this is the first study implicating decreased frequency of TNF-alpha-308 1/2 gene variant in patients with COPD and LC. Although these results need to be confirmed on larger cohort, they represent anew and interesting finding, not reported in other populations tested so far.