Nasal cavity and paranasal sinuses Neoplasia in canines are scarce, coming to just the 1.5% of all diagnosed cancer in this species. With reference to the total of respiratory tract´s tumors they represent between 60 and 80% of all the diagnoses. They are more common in long-nosed canines, with no preference for gender. Due to their behavior, the neoplasia developed in nasal cavity or paranasal sinuses can be both, benign or malignant, being the latter the most frequent one. Taking into account the origin tissue they may be epithelial, of connective tissue, and from some other origin as lymphomas and the transmissible sexual tumor. The symptoms onset is associated with the ability of obstructing the airways and the local invasion and destruction of tissue. In general, clinical associated signs consist mono or bilateral difficulty to breath, sneezing, nasal discharge, nose bleeding and masses of varied size and shape. The diagnosis is based on the symptoms appearance and cytologic and histological evaluation of injuries, being the latter 100% diagnostic. The treatment consists in the surgical extraction combined with radiation therapy and chemotherapy.