To find the influence of genetic polymorphisms of glutathione S-transferases M1 (GSTM1) and T1 (GSTT1) on hematological parameters in smoker and non-smoker subjects, the present study was done. This cross-sectional study was conducted on 97 healthy males (24 smokers, 73 non-smokers). The genotypes were determined using a polymerase chain reaction based method. In non-smokers, there was no statistically association between number of active genes and the study parameters. However, in smokers, RBC count was significantly decreased in null genotypes of GSTT1 (t = 3.021, df = 22, P = 0.006) and GSTM1 (t = 2.141, df = 22, P = 0.044). Also, in smokers, RBC count significantly decreased in persons having GSTM1 and GSTT1 null genotypes in comparison with subjects having two active genes (F = 5.554; df = 2, 21; P = 0.012). Because elevated RBC count correlate well with risk of coronary heart disease, it might be concluded that GSTM1 and GSTT1 null genotypes have protective role(s) for developing coronary heart disease.