The objective of the present work was to address earlier diagnostics of benign and malignant tumours in the nasal cavity and paranasal sinuses with a view to its improvemen. The immunohistochemical study and the analysis of its results made possible not only differential diagnostics of the tumorigenic processes in the nasal cavity and paranasal sinuses but also the estimation of the qualitative potential of each neoplasm. The immunohistochemical study demonstrated that the development of cancer of the nasal cavity and paranasal sinuses was associated with a substantial increase in the proliferative activity of epithelium and the appearance of a large amount of the mutant P53 protein in the atypical cells. The cells of inverted papilloma and unaffected epithelium exhibited only weak proliferative activity, contained cytokeratin-8 in their cytoplasm, and did not express a pathological receptor protein at the cytoplasmic membrane surface.