We have investigated the functional state of the mucous membrane of the nasal cavity and maxillary sinus after radical and minimally invasive surgical procedures during the log-term postoperative period, i.e. three and more months after the intervention. The materials for the study were brushings and histological biopsies; in addition, the functional parameters of the mucous membranes of the nose and maxillary sinuses were estimated before and after surgery. It has been found that the type of the surgical intervention on the inferior turbinate bones for the treatment of chronic rhinitis, such as gentle turbinotomy, has no significant influence on the state of the mucous membrane. The study has demonstrated that 48% of the patients presenting with the chronic maxilloethmoidal mixed form of sinusitis experience epithelial metaplasia resulting in atrophic scarring of the mucosa whereas in the remaining 52% the ciliary epithelium becomes either damaged or detached and the ciliary beat frequency (CBF) decreases. In the exudative form of the disease, CBF and some other functional characteristics are improved but the stromal oedema persists and ciliated epithelium integrity gets compromised.