Chronic obstructive pulmonary disease (COPD) affects a large number of patients in the world and is associated with significant morbidity, disability and mortality. Exacerbations of COPD are a major cause of morbidity, mortality and hospital admission. During COPD exacerbations, airway inflammation shows some features of Eosinophilic inflammatory processes, with recruitment of eosinophils. The aim of our study was to investigate whether ECP, released by activated eosinophils, concentrations could be a useful marker in the diagnosis of COPD exacerbations. This study included 88 individuals: 30 patients with acute COPD exacerbations (ECOPD), 15 patients with mild to moderate stable COPD (COPD I-II), 15 patients with severe to very severe stable COPD (COPD III-IV) and 30 healthy controls (11 non-smokers and 17 healthy smokers). The levels of eosinophil cationic protein (ECP) was determined by ELISA. The results showed that serum ECP was significantly increased in COPD patients (31.314 ± 11.361 ng\ml) compared with healthy controls (6.579 ± 2.685 ng\ml). COPD exacerbations showed also significant increased levels of serum ECP (39.195 ± 10.246 ng\ml) compared to stable COPD I-II (20.722 ± 3.343 ng\ml) and stable COPD III-IV (26.144 ± 5.799 ng\ml). But there was no significant differentiation among stable COPD groups (P=0.311). This indicates the systemic inflammation associated with COPD and suggest the possibility to use serum ECP as a diagnostic biomarker and to evaluate the inflammatory response in COPD exacerbations.