The purpose of the present study is to report four cases of sinonasal hemangiopericytoma (HP) diagnosed and treated in our department between 1987 and 1998. The pretreatment findings and the treatment are described and discussed in the light of the literature. HP are unusual vascular tumors, featuring pericytes distributed around normal vascular channels. Two of these four cases were located in the nasal cavity and the other two were located in the maxillary sinus. Inside the nasal cavity, HP presented as a protruding reddish-gray mass with marked bleeding on contact. Electron microscopy and immunohistochemical techniques are essential for diagnosis and to distinguish HP from other sarcomatous tumors. Preoperative assessment included routine CT, MRI, arteriography and selective embolization. These tumors must be treated surgically with complete excision. An endonasal approach was performed in two cases of intranasal HP, while a combined external-endonasal approach was required for the other two cases of HP.