Based on the experimental studies of Seidegård et al. [33], as well as the results of Lee et al. [34], concerning the effects of the null variant of GSTM1 and GSTT1 genes on enzyme activity and enzyme protein levels, we suggest that the loss of enzymatic activity in COPD patients that carry the null GSTM1 variant results in altered antioxidant defense and the detoxification of ROS and their products. This evidence concerns the gene GSTM1 and chronic obstructive pulmonary disease.