The use of intravenous (i.v.) contrast media in CT examinations is often of great value in improving diagnostic accuracy. The preferable route of administration is via a peripheral i.v. cannula, with powered injectors allowing reliable delivery of rapid flow rates. However, many patients with a pre-existing central venous access device may have difficult peripheral access and there is a temptation to use the central device for delivery of contrast media. This review summarises the available evidence for the safe and effective use of these devices to assist the radiologist in balancing the relative risks and benefits of their use for contrast medium injection.