It was a randomised, double-blind, placebo controlled comparative study of the clinical symptoms and chosen parameters of ventilation of inhaled ambroxol in patients hospitalized with exacerbation of chronic obstructive pulmonary disease (COPD). Eligible patients--30 patients (13 men and 17 women) aged of mean value 70.5 +/- 6.9 years who fulfilled the clinical traits of exacerbation of chronic bronchitis entered the study. 15 patients were treated with inhaled ambroxol and 15 were treated with placebo. Moreover all patients were treated with concomitant medications typical for exacerbation of COPD (systemic steroids, intravenous infusions with euphillin, antibiotics, Berodual nebulizations and oxygen therapy). Spirometry and data related to clinical symptoms were taken at the beginning of the study and after 1 and 3 days and after the end of the treatment. At the end of the treatment period in both groups (inhaled ambroxol therapy vs. placebo) there wasn't found statistically significant difference in the number of cough and dyspnoe attacks. There was found the difference in FEV1 and FEF 50 in both groups, but improvement in patients treated with ambroxol was statistically significantly faster, that can influence the cost of treatment. Moreover there were not found important adverse events in ambroxol group.