Although the clinical pictures of asthma and chronic obstructive pulmonary disease (COPD) may be similar, the pathogenesis differs in many aspects. The aim of the present study was to compare the cellular and biochemical features of airway inflammation in patients with asthma and COPD. The study was conducted in 22 patients with asthma (M/F 12/10, mean age 36 +/-14 years) and 17 patients with COPD (M/F 10/7, mean age 57 +/-11 years). Each patient underwent sputum induction followed by bronchoscopy, and bronchoalveolar lavage. Total and differential cell counts and the concentration of interleukin-8 (IL-8) and myeloperoxidase (MPO) were measured in induced sputum (IS) and BALF. We found no significant differences in the total and differential cell counts in IS between asthma and COPD patients. However, COPD patients showed an increased total macrophage count in BALF compared with asthma patients. The relative eosinophil count in BALF was significantly higher in patients with asthma vs. COPD. The concentration of IL-8 in IS and BALF was significantly higher in patients with COPD vs. asthma patients. The BALF concentration of MPO was significantly higher in patients with COPD compared with asthma patients. We conclude that the comparison of cellular composition and the concentration of inflammatory mediators in IS does not differentiate between asthma and COPD. The evaluation of BALF reveals more differences in the cellular and biochemical features of airways inflammation in patients with asthma and COPD than that of IS.