Diagnostic tests in patients complaining of carpal tunnel syndrome (CTS) are based on physical examination, electrodiagnostic tests (EDTs), and diagnostic imaging. Timely diagnosis helps prevent permanent nerve damage and its sequelae in terms of functional impairment. Imaging provides additional information to that obtained from clinical tests and EDTs. By allowing direct visualization of the compressed median nerve (MN), ultrasound (US) and magnetic resonance imaging can depict the causes for secondary CTS and describe anatomical variants, such as a bifid MN or a persistent median artery of the forearm, as well as space-occupying lesions including tenosynovitis and ganglion cysts. In addition, diagnostic imaging is of value for postoperative patients presenting with persistent symptoms. Finally, US is able to add information for EDT-negative symptomatic patients. Over time, US has increased in its sensitivity and specificity so it can be used as the initial test in patients presenting with clinical symptoms of CTS because it is now equivalent to EDT. The use of US as a screening test may reduce the number of EDT examinations in patients with suspected CTS, providing additional valuable anatomical information.