Chronic paranasal sinusitis is usually caused by recurrent infection. The case of sinusitis due to craniofacial trauma is rare. Hemosinus due to craniofacial trauma can be resolved by mucociliary clearance within weeks. If the ostium of sinus were traumatized, it might become an etiologic factor of chronic sinusitis. Two cases of craniofacial trauma due to motor vehicle accident were studied at our hospital from 1994 to 1995. Hemosinuses were noted in each case. During hospitalization, they were complicated by acute sinusitis. Three of four sides of sinusitis were cured after management, and one side of sinus due to severe trauma of medial wall gave rise to chronic sinusitis within months.