Our results did not support this finding: we confirmed the results obtained by other authors [19–22] that the MMP-9 level in serum of COPD patients is higher in serum than in healthy controls, but we found that the difference does not depend on the SNP rs3918242, as well as on the number of MMP-9 gene copies (Table 4). This evidence concerns the gene MMP9 and chronic obstructive pulmonary disease.