Ultrasonography and scintigraphy are the first line diagnostic imaging modalities for the evaluation of thyroid nodules. Scintigraphy provides functional informations, mainly detection of hot nodules. US provides accurate morphologic evaluation and it may sometimes suggest malignancy. US is the modality of choice for follow-up of non resected nodules and is very useful for guidance during biopsy. CT and MRI are mainly used for preoperative evaluation of thyroid nodules.