Background: Airway bacterial colonization by potentially pathogenic microorganisms occurs in a proportion of patients with Chronic Obstructive Pulmonary Disease (COPD). It increases airway inflammation and influences outcomes negatively. Yet, its diagnosis in clinical practice is not straightforward. The electronic nose is a new non-invasive technology capable of distinguishing volatile organic compound (VOC) breath-prints in exhaled breath. We aim to explore if an electronic nose can reliably discriminate COPD patients with and without airway bacterial colonization. Methods: We studied 37 clinically stable COPD patients (67.8 +/- 5.2 yrs, FEV1 41 +/- 10% ref.) and 13 healthy controls (62.8 +/- 5.2 yrs, FEV1 99 +/- 10% ref.). The presence of potentially pathogenic microorganisms in the airways of COPD patients (n = 10, 27%) was determined using quantitative bacterial cultures of protected specimen brush. VOCs breath-prints were analyzed by discriminant analysis on principal component reduction, resulting in cross-validated accuracy values. Area Under Receiver Operating Characteristics (AUROC) was calculated using multiple logistic regression. Results: Demographic, functional and clinical characteristics were similar in colonized and non-colonized COPD patients but their VOC breath-prints were different (accuracy 89%, AUROC 0.92, p > 0.0001). Likewise, VOCs breath-prints from colonized (accuracy 88%, AUROC 0.98, p < 0.0001) and non-colonized COPD patients (accuracy 83%, AUROC 0.93, p < 0.0001) were also different from controls. Conclusions: An electronic nose can identify the presence of airway bacterial colonization in clinically stable patients with COPD. (C) 2014 Elsevier Ltd. All rights reserved.