Angiotensin converting enzyme inhibitors (ACE-I) are generally-applied medicaments in treatment and prevention of many illnesses. Although they are generally well-tolerated by an organism, their application might cause side-effects in a respiratory system, such as: dry cough, angioedema. They can also cause or strengthen bronchospasm. In this paper we analyse mechanism responsible for ACE-I side-effects concerning the respiratory system. The paper also highlights a positive effects of lung fibrosis and reduction of pneumonia risk in elderly people.