The objective of the preset study was to elucidate the mechanisms of local protection of the mucous membrane of the nasal cavity and paranasal sinuses based on the results of original morphological investigations. The materials for the study were obtained at autopsy on the patients who had died from the diseases unrelated to otorhinolaryngological pathology. The preparations for histological and immunohistochemical studies were obtained by routine staining techniques. Moreover, some immunohistochemical studies were carried out with the use of monoclonal antibodies against specific markers of macrophages, T- and B-lymphocytes. It was shown that the mucous membranes of the nasal cavity and paranasal sinuses contain mucociliary, lymphoepithelial, mucoglandular, and stromal-vascular (interstitial) barriers totally different in terms of structural and functional characteristics. Under normal conditions, these barriers serve to protect mucosa at different levels. At the same time, functional or structural disturbance of one of the superficially located mechanisms of local protection induces activation of another.