Mucoceles of the sphenoid sinus represent 1-2% of all paranasal sinus mucoceles. The aim of this paper is to report our experiences in patients with mucoceles of the sphenoid sinus.In a period of 4 years, we observed six patients in whom a mucocele of the sphenoid sinus was suggested pre- or intraoperatively. Symptoms and signs included headache, visual loss and palsies of the III and VI cranial nerve. All patients were investigated by MRI and/or CT. Imaging findings were compared with operative and/or histological findings.In three cases there were simple mucoceles, in one case we found a tumour (nasopharyngeal carcinoma) associated mucocele and in two cases, malignant tumours (carcinoma, chordoma) imitated a mucocele. The diagnosis of simple mucoceles was no problem at all by imaging. Difficulties made the two malignant tumours and the tumour associated mucocele. In the first two cases, repeated histological samples were necessary to make the final diagnosis.Mucoceles of the sphenoid sinus should be investigated and handled very carefully with regard to differential diagnoses and tumour associated cases.