Bronchiectasis (BE) is still an important cause of chronic supurative respiratory diseases in developing countries. Neutrophil-derived proteases such as neutrophil elastase and matrix metalloproteases (MMPs) are implicated in causing airway damage in chronic pulmonary disease. In this study, we aimed to evaluate the MMP-9 and its natural tissue inhibitors of metalloproteinases (TIMP-1) levels utilizing the exhaled breath condensate (EBC) method and their relationship with radiological findings and pulmonary functions in children with BE. Thirty-eight children with BE and 12 healthy children were included: Group 1 (cystic fibrosis [CF] BE), Group 2 (non-CF BE), Group 3 (control group). High-resolution computerized tomography (HRCT) scores were calculated according to the anatomic extent of BE. Pulmonary function tests were performed, and MMP-9 and TIMP-1 levels in EBC were analyzed by ELISA. Exhaled breath condensate MMP-9 level was 48.9 +/- 26.8 ng/ml for Group 1, and for Group 2, 42.8 +/- 18.1 ng/ml; and for Group 3, 30 +/- 3.7 ng/ml. Although no statistically significant difference was found between the Groups 1 and 2, a significant difference was detected between these groups and controls. No statistically significant difference was found in TIMP-1 levels regarding all groups. EBC MMP-9 levels were inversely correlated with pulmonary functions test, and positively with HRCT scores and annual number of pulmonary infections. In conclusion, this study showed that EBC of children with both CF BE and non-CF BE contained higher levels of MMP-9 in comparison to controls. We suggest that EBC MMP-9 level may be a useful marker of airway injury in patients with BE however prospective studies are needed. Pediatr Pulmonol. 2009; 44:1010-1016. (C) 2009 Wiley-Liss, Inc.