Adverse drug reactions is an important healthcare issue, it causes excess morbidity and mortality. The aim of this study was to determine the adverse drug reactions in patients who admitted to the outpatient clinic of respiratory diseases and to improve some clinical strategies if they are preventable.This study is a prospective observational study which was performed to determine adverse drug reaction in patients who admitted to the outpatient clinic of respiratory diseases.During the 15 months of study period a total of 114 adverse reactions were reported in 92 out of 18.130 patients. Most of the adverse reactions were related with gastrointestinal system, central nervous system and cardiovascular system. The most of the adverse events were associated with fixed inhaled formoterol-budesonide combination and inhaled tiotropium. The most frequently reported reactions were hoarseness, xerostomia, headache and dizziness. Poliuri and cough were less frequently reported reactions.Most of the adverse reactions were of limited intensity but some of these side effects might effect patients compliance. Serious adverse events were not detected.