Objective: We prospectively investigated the correlation between response to the treatment and age and disease duration in asthmatic patients with predicted FEV1 of 50-80 %, according to changes in FEV1 parameter. Material and Methods: Eighty patients completed the study. All patients regularly utilized 800-2000 mcg/day inhaled Budesonide and 100 mcg/day inhaled Salmeterol for three months. The patients' response rate to the treatment was calculated by comparing their initial and final FEV1 values. The statistical correlation between these response rates and patients' age [18-40 years of age (n:25); 41-60 years of age (n:37) and older than 60 years of age (n:18)] and disease duration [1-5 years (n:20); 6-10 years (n:18); 11-15 years (n:15); 16-20 years (n:14); longer than 20 years (n:13)] was investigated in a stepwise manner. Results: By evaluation of final FEV1 values and response rates to the treatment found by the difference between initial and final FEV1 values, no difference could be detected between 18-40 years of age and 41-60 years of age groups (p>0.05), but the values in both groups were found to be better than the older than 60 years of age group (p<0.05). Five groups, divided according to the disease duration, had the same response rate to the treatment (p>0.05); in comparison of the final FEV1 values, the first group was found to be better than the fifth group (p<0.05). In conclusion, response to the treatment of asthmatic patients older than 60 years of age and with longer than 20 years of disease duration was found to be comparably limited than the patients who were younger and having a disease duration of 1-5 years. Conclusion: We think that in the treatment of such patients, higher doses of inhaled drugs and/or therapeutic combinations including increased number of drugs should be preferred.