The present morphological study was based on the analysis of materials obtained during the surgical treatment of 64 patients aged from 15 to 68 years presenting with long-term chronic purulent maxillary sinusitis. All the patients had been inadequately treated with antibacterial preparations during the pre-hospitalization period. It was shown that the patients developed well-apparent pathomorphological changes in maxillary sinus mucosa that promoted chronization of the inflammatory process.