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 to liver efficiency. Methods: This study was done in Kirkuk province. It was conducted on (75) healthy male subjects, their ages ranged from 20 to 40 years. They were divided into three groups; 25 heavy smokers, 25 moderate smokers, and 25 non-smokers. Blood was withdrawn for estimation of serum liver function test, lipid profile, and protein electrophoresis. Results: There were statistically significant elevations in serum alkaline phosphatase (ALP), alanine transaminase (SGPT) and aspartate aminotransferase (SGOT) activities in heavy smokers while serum total bilirubin significantly was lower compared to nonsmokers. Serum total protein and albumin were significantly lower in heavy smokers comparing to non-smokers. The results of serum protein arose gel-electrophoresis showed significant changes in serum protein fractions in smoker groups. The mean level of serum total cholesterol, triglyceride, LDL, and VLDL 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 dependent.