The rate of direct smoking, second hand smoking, and smokeless tobacco users as well as the amount of environmental pollutant like polycyclic aromatic hydrocarons is increasing in Bangladesh. Therefore, the prevalence of lung cancer is increasing day by day. To the best of our knowledge, no pharmacogentic study of CYP3A4, CYP3A5 genes has been reported on Bangladeshi population relating those with lung cancer. The present study was conducted to determine the association of CYP3A4, CYP3A5 gene polymorphisms and tobacco smoking in the development of lung cancer in Bangladeshi population. A case-control study was carried out on 106 lung cancer patients and 116 controls to investigate three allelic variants-CYP3A4*1B, CYP3A5*3, and CYP3A5*6 using Polymerase Chain Reaction Restriction Fragment Length Polymorphism. Risk of lung cancer was estimated as odds ratio (OR) and 95 % confidence interval (CI) using unconditional logistic regression models. The variant allele frequencies for CYP3A4*1B (*1A/*1B + *1B/*1B) were 2.83 % and 0.86 % and that of CYP3A5*3 (*1A/*3 + *3/*3) were 88.68 % and 85.34 % in cases and controls, respectively. Individual carrying at least one variant allele of CYP3A4*1B (CYP3A4*1A/1B + *1B/1B) has a 3.35 times more risk (OR = 3.35, 95 % Cl = 0.34-32.71, p = 0.271) for developing lung cancer whereas individual carrying at least one variant allele of CYP3A5 (CYP3A5*1A/3 + *3/3) has a 1.26 times more risk (OR = 1.35, 95 % Cl = 0.61-2.97) and both are statistically non-significant (p > 0.05). CYP3A5*6 was absent in the study population. No association of lung cancer with the mentioned polymorphisms was found both in heavy and light smokers. In the cases of all three major types of lung cancer-squamous cell carcinoma, adenocarcinoma, and small cell carcinoma-significantly strong relationships (p ˂ 0.05) have been found. To confirm the association of lung cancer with the mentioned polymorphisms, large number volunteers (patients and controls) will be required.