Documentation of the psittacine paranasal sinuses has been limited. To provide more published detail, spiral computed tomography (CT) was used to scan the cephalic and cervical region from cadavers of 10 psittacine birds (Ara ararauna, Ara chloroptera, Ara macao, and Anodorhynchus hyacinthinus). Skeletal studies, histologic examinations, and evaluation of deep-frozen sections and anatomic preparations confirmed the results of the CT scans. New morphologic details of the paranasal sinus and some compartments were discovered. The paranasal sinuses of these macaws consist of two unpaired rostral compartments, followed caudally by eight paired compartments. Histologic examinations revealed that the walls of the paranasal sinuses consist of flat or cubic monolayer epithelium with underlying connective tissue. The described method of CT examination of these macaws, especially the positioning, scan orientation and parameters, and documentation of the normal paranasal sinus, provides a basis for future clinical use of CT.