Introduction: Electron microscopy (EM) has been clinically used with success, although few attention has been given in ultrastructural aspects of superior airways mucosa. Objective: We aim to evaluate the ultrastuctural and histologic aspects of the mucous membrane of inferior turbinate and maxillary sinus of patients with chronic maxillary rhinosinusitis (CMR). We used fragments of mucous membrane from inferior turbinate and maxillary sinus of 8 patients, being 3 normal and 5 with CMR. The fragments were prepared for EM and optic microscopy (OM) observation. Histologic characterization and morphometric study at ultrastuctural and histopathological level were performed considering many qualitative and semi-quantitative parameters. Results: The alterations of the mucous membrane observed in EM were unspecific and expressed the consequences of a chronic irritation; there were many structural and numeric abnormalities; comparing with the normal ones, the inflammatory lesions of the maxillary sinus were more important; in the inferior turbinate, the fibrosis was also more important; rhinosinusitis was characterized by the change in the site of mucous production, from the glands to the secretory cells. Finally, OM, when done by quantitative methods and morphometry, permits a wide evaluation of inferior turbinate and maxillary sinus mucous membrane rather than EM.