Eosinophilic airway inflammation is regarded as a typical feature of asthma, while in chronic obstructive pulmonary disease (COPD) neutrophils seem predominant inflammatory airway cells. The aim of the present study was to compare the cellular components of airway inflammation in patients with newly diagnosed mild or moderate COPD and asthma. Seventeen patients with COPD (M/F 10/7, aged 57 +/-11 yr) and 22 patients with asthma (M/F 12/10, aged 36 +/-14 yr) were enrolled into the study. None of the patients has been treated with steroids for at least 3 months. All patients underwent clinical examination, laboratory examinations, skin-prick tests, pulmonary function tests, methacholine challenge test, and sputum induction with the total and differential cell count assessments. We found increased number of eosinophils in both study groups. However, there were no significant differences in the cellular composition of induced sputum between the asthma and COPD patients. We conclude that eosinophils are important inflammatory cells not only in asthma, but also in COPD.