An important factor in the preoperative evaluation of patients with invasive periorbital carcinomas is the presence or absence of orbital bone involvement. A retrospective study was performed to evaluate the reliability of computed tomography (CT) in detecting orbital bone invasion. Eleven patients with extensive facial-orbital basal cell or squamous cell carcinomas were evaluated preoperatively by CT and the results were compared with the clinical findings and postoperative histopathologic findings. Of the seven cases in which histopathologic examination confirmed bone and/or periosteal invasion, CT was positive in three (43%). Based on these findings, we strongly recommend that CT not be relied upon in excluding orbital bone involvement. Bony invasion may be histologically present, even though destruction is not seen on CT scans. Therefore, a normal CT scan should not deter one from removing clinically abnormal bone or periosteum and submitting it for histologie examination.