Background: To show that during the exarcerbration of asthma and COPD, increased airway resistance is accompanied with decreased spirometry values (FVC, FEV1, FEF50, and PEF) also comes increasing of airway resistance (RAW). Patients and methods: This research included 74 patients, in exacerbation phase of disease. All the patients got spirometry and plethysmography measurements, including adequate therapy, and after at least one month on control examination they repeated spirometry and plethysmography and answered a short life questionnaire. Results: The mean value of RAW after therapy in asthma is decreased for -17. 68% and in COPD for -15. 44%. The mean value of RAW in all levels of obstruction is higher in COPD than in asthma, before and after therapy. After therapy spirometry values (FVC, FEV1, FEF50, and PEF) were significantly increased in asthma than in COPD. From questionnaire analyses 78.37 %(58) of patients felt well, 17.57 %(13) felt the same like before therapy and 4.05 %(3) of them felt worst. All the patients who felt worst were in COPD group of patients. All of them had increased RAW, almost all felt better (96. 43%) had decreased RAW. In asthma nobody felt worst. In most of the patients (76.67%) who felt better RAW was decreased. Conclusion: Adequate therapy during exacerbation of asthma and COPD decreases value of RAW and increases spirometry values. Increase in spirometry values in asthma is much higher than in COPD. Mean values of resistance in COPD are higher before and after therapy than in asthma. There is a negative relationship between subjective experience of illness and the level of resistance. Measuring of RAW can be a good parameter for monitoring COPD and asthma control. [Med Arch 2011; 65(5.000): 270-173]

exacerbation of asthma or COPD, spirometry, airway resistance – Raw