Olfaction not only contributes to our quality of life but, among other functions, it is also necessary for identifying potential dangers, e.g., fire or spoilt food. In general the value of olfaction is only recognized when the sense of smell is impaired or lost. Olfactory dysfunction is diagnosed according to its cause (e.g., sinonasal, post-traumatic, post-upper respiratory tract infection, neurodegenerative, and idiopathic). At present little is known about prognostic factors for predicting resolution of olfactory loss on an individual basis. In cases of impaired olfaction due to sinonasal disease, both conservative and operative treatments have been established. Corticoids are used both topically and systemically. In cases of severe mechanical obstructions or advanced stages of nasal polyposis, FESS (functional endoscopic sinus surgery) seems to be the state of the art.