Background and objective:Cigarette smoking is one of the 10 greatest contributors to global death and disease. Cigarette smoke consists of many chemicals, including cytotoxic, carcinogenic and free radicals, therefore it affects many organs if not all.This work is directed to evaluate the effects of dose response patterns of tobacco exposure on liver tissue, through assessing some serum biochemical parameters related with liver efficiency. Methods: This study was done in Kirkuk province. It was conducted on (110) healthy male subjects, their ages ranged from 20 to 40 years. They were divided into three groups; 40 heavy smokers, 30 moderate smokers and 40 non-smokers. Blood was withdrawn for estimation of serum liver function test, lipid profile, protein electrophoresis, and lipid peroxidation test (Serum Malondialdehyde; MAD level). Results: There were statistically significant elevations in serum alkaline phosphatase (ALP), alanine transaminase(GPT) and aspartate aminotransferase(GOT) activities in heavy smokers while serum total bilirubin significantly was lower comparing to non smokers. Serum total protein and albumin were significantly lower in heavy smokers comparing to non smokers. The results of serum protein agarose gel-electrohporesis showed significant changes in serum protein fractions in smoker groups. The mean level of serum total cholesterol, triglyceride, LDL, VLDL and malondialdehyde was significantly higher in heavy smoker group, while serum HDL level had a significantly lower value. Conclusion: Cigarette smoking can affect liver efficiency and functions. These effects are dose exposure depenent. Keywords: Cigarette smoking, Liver function test, Liver enzymes, MAD, Lipid profile.