Forty-five computed tomographic examinations were performed on 34 patients with diseases of the paranasal sinuses and their adjacent structures. Coronal sections were obtained in addition to transverse axial tomographic sections. Evaluation was made whether CT could provide more informations compared with plain roentgenography and whether there were additional informations on coronal sections. CT showed soft tissue abnormality and its extension to better advantage. Especially, involvement of the orbits, pterygoid fossa, nasopharynx, skull base and brain were shown well. Coronal sections were useful in evaluation of superior and inferior extension of the tumors such as involvement of the superior and inferior orbital walls and skull base as well as intracranial extension. Since CT has the ability to better define the total extent of the lesion, this technique should be added to the conventional roentgenologic techniques preferably with the use of coronal sections.