Background: The aim of the present study was to investigate the effects of opium addiction and cigarette smoking on the complete blood count (CBC).Methods: Eighty-six male subjects, including 31 opium-addicted cigarette smokers (OACS), 19 opium-addicted non-cigarette smokers (OANCS), 17 non-opium-addicted cigarette smokers (NOACS), and 19 non-opium-addicted non-cigarette smokers (NOANCS) participated in this study. The CBC test was measured in all individuals.Findings: The OACS had significantly higher white blood cell (WBC), lymphocyte, and red blood cell (RBC) count but lower in mean corpuscular volume (MCV) compared to NOANCS. The OANCS had significantly higher lymphocyte in comparison with NOACS. Our results demonstrated that the number of WBC, lymphocytes, and RBC were significantly higher, while, MCV was lower in OANCS subjects when compared to NOACS. The OACS had significantly higher level of lymphocyte in comparison with NOACS. The mean number of lymphocyte in OANCS was found significantly higher than NOACS. The smokers were shown to have significantly higher levels of WBC compared to NOANCS.Conclusion: Our results showed that opium-addiction, especially when associated with cigarette smoking, has intensive effects on hematological factors and these alteration might leads to greater risk for developing atherosclerosis, cardiovascular diseases, and imbalance in immune system.