Chronic rhinosinusitis (CRS) is an inflammatory disease affecting the nose and paranasal sinuses. Fungi are considered to be one of the pathogens responsible for some kinds of CRS. Fungal rhinosinusitis – the classifications schemes, the diagnostic criteria and methods of treatment are still being discussed. 338 patients underwent the endoscopic sinus surgery due to CRS in the Otolaryngology Department of the Medical University of Lodz in the years 2009–2011 (February). The histopathological examination revealed fungi only in three patients. The authors report three cases of patients with fungal rhinosinustis – the fungal ball of the sphenoid sinus in one patients, the fungal ball of the maxillary sinus in the second one and non-invasive fungal rhinosinusitis. The different classifications and diagnostic criteria are also presented. Based on the publications using updated diagnostic standards and sensitive techniques to detect fungi, a higher number of patients can now be diagnosed with fungal rhinosinusitis.