purpose: to describe the ct findings of orbital cellulitis due to sinusitis. methods: the records and ct scans of 45 consecutive patients with orbital cellulitis due to sinusitis treated at the hospital of the medical school of ribeir？o preto were analyzed by a radiologist and two orbital surgeons. results: three major types of ct changes were observed: diffuse fat infiltration, subperiosteal abscess and orbital abscess. diffuse fat infiltration (characterized by an increased density of the extra- or intraconal fat) was seen in 11 patients (24.44%). a subperiosteal abscess was diagnosed in 28 patients (62.23%). a surgically proved orbital abscess was detected in 6 patients (13.33%). conclusions: in all cases of orbital cellulitis due to sinusitis intraorbital changes can be detected by ct scans either as a diffuse infiltration of the orbital fat or as a detachment of the periorbita (subperiosteal abscess) or a true orbital abscess. category i of chandler orbital cellulitis classification (inflammatory edema) must be understood as a stage of a process that is already happening within the orbit and, as the term "preseptal cellulitis" means a palpebral infection, this designation should not be used to stage orbital cellulitis.