Background: liver function can be affected by many factors; the proposed effects of diabetes and smoking in liver function require a comprehensive evaluation. This study was conducted to compare the effect of these factors on liver enzymes in Sudanese population. Method: activity of liver enzyme AST, ALT and ALP were estimated in 235 volunteer (75 smokers, 75 diabetic patients and 85 normal individual as control). Results: Mean±SD of AST, ALT and ALP of smoker were (14±5.9), (27±13) and (105±18.9) respectively, and of diabetic were (25±7.8), (28±5.8) and (130±20) respectively, which were higher compared to control groups (15.5±4.6), (23±5.1), and (88.3±16.7), respectively, P.value= 0.000. Conclusion: The findings advise that both cigarette smoking and diabetes have effects in liver function leading to variable alteration in liver enzyme activity.