Imaging studies play a central role in diagnosing and monitoring giant-cell and Takayasu arteritis. Deep, large vessels can be examined by CT or MRI, while colour Doppler ultrasound and MRI have been used with promising results to investigate the temporal arteries. Positron emission tomography is very sensitive in detecting large-vessel inflammation, although it does not delineate the vessel wall. Imaging procedures can also be used to monitor the disease course. However, imaging signs of inflammation may sometimes persist despite clinical remission and, conversely, seemingly unaffected vessels may develop alterations later on.