Background: Cigarette smoking is awell-known significant contributor to the development of many illnesses that having an inflammatory component. Smoking has both acute and chronic effects on haematological parameters. Objective: to assess the impact of cigarette smoking on complete blood count (CBC) indices and some inflammatory markers erythrocytic sedemitation rate (ESR) and C-reactive protein(CRP). Methodology: this case-control study was conducted on 30 healthy active smokers and 30 healthy passive smokers and 30 age and sex-matched healthy non-smokers subjects. Data regarding age, sex, smoking index, and smoking duration were recorded. CBC, differential leucocytic count, platelets/lymphocytes ratio (PLR), neutrophils/lymphocytes ratio (NLR), CRP and ESR were measured. Results: A statistically significant differences were identified between active and passive smokers groups regarding CBC and inflammatory markers parameters except for neutrophil %. ESR and CRP had no statistically significant difference. Statistically, significant differences have been identified between active smokers group and control group regarding all CBC indices and inflammatory markers e.g PLR, NLR, ESR and CRP, while no statistical difference has been identified between passive smokers group and control group regarding CBC and inflammatory markers parameters except monocyte % and ESR, which had statistically significant difference. Conclusion:Passive smoking affects hematological indices and inflammatory markers as well as active smoking. Accordingy, it is important to keep in mind that cigarette smoking either active or passive is one of differential diagnoses of change in blood indices.