Computed tomography (CT) has revolutionised the diagnosis and management of ocular and orbital diseases. The use of thin sections with multiplanar scanning (axial, coronal and sagittal planes) and the possibility of three-dimensional reconstruction permits thorough evaluation. To make the most of this technique, users must familiarize themselves with the pertinent CT principles and terminology. The diagnostic yield is optimal when the ophthalmologist and radiologist collaborate in the radiodiagnostic workup. In this article we describe a systematic approach to the interpretation of ocular and orbital CT scans.