The article presents clinical observations of patients with complaints of difficulty in nasal breathing due to Thornwaldt cyst, incidence of which among the nasopharyngeal abnormalities is 4%. Morphological substrate of this nosology is the encapsulated nasopharyngeal cavity, which is formed after the 10th week of embryogenesis while maintaining the connection of the chord’s pharyngeal segments with the entoderm. For a long time, the cyst is characterized by an asymptomatic course, manifested clinically in 10% of cases when inflammation occurs, characterized in such cases by impaired nasal breathing, thick mucus drip on the posterior wall of the pharynx, as well as possible subfebrility, headache in the parietal and occipital regions, bad breath, hypernasal voice, rhonchopathy, lymphadenopathy; additionally, congestion and «tinnitus», hearing loss are possible. The importance of endoscopic and radiological diagnostic methods in the examination of patients with retronasal obstruction associated with auditory tube dysfunction and postnasal drainage is shown. Endoscopic marsupialization of the nasopharyngeal cyst in such cases allows to eliminate retronasal obstruction, restore nasal breathing and ensure regression of associated symptoms, primarily manifestations of tubal dysfunction and postnasal drip.