During the last decades, cytogenetic markers in peripheral blood lymphocytes have been used to assess exposure to carcinogenic or mutagenic agents. This study was conducted with the aim of assessing the use of micronucleus [MN] assay as a marker in lung cancer and whether this method could predict cancer risk in patients with chronic obstructive pulmonary disease [COPD] as it is known that lung cancer is far more common in patients with COPD than in those with normal airflow. The study included 96 male subjects; 40 patients with lung cancer, 36 patients with COPD and 20 control subjects. Twenty five percent of cases with lung cancer and 86.1% of cases with COPD had MN frequency ranging from < 5-<15 MN/500 cytokinesis blocked [CB] binucleated cells compared to 100% in the control group. Forty percent of cases with lung cancer and 13.9% of cases with COPD had 15-20 MN/500 CB binucleated cells. Thirty five percent of cases with lung cancer had 20-25 MN/500 CB binucleated cells. These differences are statistically significant [X2= 75.2, p < 0.000]. In the lung cancer group, the mean MN/500 CB binucleated cells was 18.4±4.2 [range:12-27 MN/500 CB binucleated cells], in the group with COPD, the mean MN/500 CB binucleated cells was 8.3+4.1 [range:1-17 MN/500 CB binucleated cells] with 8 patients [22.2%] having MN in the cancer range, i.e. 12-17. The mean MN/500 CB binucleated cells of the control group was 5.4±2.5 [range:2-12 MN/500 CB binucleated cells]. These differences are statistically significant [least significant difference test]. All cases with lung cancer/and 63.9% of cases with COPD had mean MN frequency greater than the upper 95% CI of the mean MN frequency for the control group. Applying logistic regression analysis for the effect of risk factors revealed that lung cancer patients who were current or ex smokers had significantly higher MN frequencies than patients with COPD. The elevated levels of micronuclei in patients with lung cancer implies that micronucleus assay could be used as a method to detect cancer. Patients suffering from COPD who have elevated levels of micronuclei need to be followed up closely.