According to national and international clinical guidelines, inhaled glucocorticosteroids (IGCS) are the most effective drugs in bronchial asthma (BA) therapy. However, IGCS do not always contribute to the full asthma control. In addition to external factors, including low adherence to medical recommendations, errors in the inhalation technique, comorbid conditions, lack of control over the effectiveness of therapeutic measures, and sometimes incorrect diagnosis, recently, much attention has been paid to pharmacogenetic mechanisms in reducing the effectiveness of asthma therapy. The article presents overview data on the pharmacogenetic features of reducing the effectiveness of inhaled corticosteroids in bronchial asthma therapy.