Within this study, we now show that both, MMP-8 and MMP-9 are increased in the serum of CF patients with CF lung disease and our results thus indicate that the previously observed increased MMP expression in bronchial tree of individuals with CF [34], [35], [36], [37] seems to be reflected in the blood compartment, revealing a potential role of MMPs as non-invasive and novel biomarkers of CF lung disease. Here, MMP9 is linked to cystic fibrosis.