Introduction. Cases of isolated lesions of the sphenoid sinus are rare. For descriptive purposes, clinicians divide them into inflammatory and non-inflammatory with prevalence of the former. Symptoms of the sphenoid sinus disease are difficult to characterise, the most common of them being vague headache and visual disturbances. Thorough preoperative evaluation of the lesion is essential – nasal endoscopy must be performed and computerised tomography or magnetic resonance imaging results analysed. The purpose of the study is to present the assessment of endoscopic surgery outcome in the own group of patients with isolated sphenoid disease. Material and methods. Clinical data of 22 subjects were analysed retrospectively. There were 5 patients with bacterial sinusitis, 6 with fungal sinusitis, 4 with allergic thickening of the mucous membrane with no evidence of bacterial or fungal infection, 2 with mucocele, 1 with sphenoid osteoma, 1 with inverted papilloma, 1 with a foreign body and 2 with cerebral fluid fistula. Each patient had preoperative nasal endoscopy and CT/MRI imaging performed. Then they underwent endoscopic transnasal sphenoethmoidectomy with removal of the lesion or closure of the fistula. The sphenoid sinus was approached through its front wall. Results. The patients’ postoperative course was uneventful. They noted improvement in all preoperative symptoms, except for bilateral oculomotor nerve paralysis in one individual, and were asymptomatic to ophthalmological examination. Conclusions. Isolated lesions of the sphenoid sinus, even very rare tumours like those presented here, can be in most cases safely approached and removed endoscopically. All risks of the method must be considered prior to the operation. High frequency of fungal sinusitis should be noted.