The identification of retained needles is essential because of their sharp structure with possible life-threatening complications. However, radiological evaluation could be challenging, especially in case of needles' relatively poor conspicuity and small dimension. This pictorial essay focuses on clinical issues (needle features, retention mechanisms and associated complications) and technical aspects (choice of the best diagnostic modality and technique) that can lead the radiologist to an earlier and proper diagnosis of needle retention in order to provide the best treatment for the patient.