Abstract: Objective: To study CT characteristic appearances of benign and malignant thyroid nodules,and evaluate the value of CT in differential diagnosis of thyroid nodules.Methods: Thirteen patients with benign thyroid nodule and fourteen patients with malignant thyroid nodules proved by operation and pathology were retrospectively analyzed.All patients were examined by CT plain scan.Among them,13 patients with thyroid carcinoma and 9 patients with benign thyroid nodules underwent thin slice enhanced CT scanning.Results: Thirteen of the 14 patients with thyroid cancer were correctly diagnosed by thyroid CT,and the diagnostic accuracy of CT was 92.9%.In 13 patients with thyroid carcinoma,vague contour of malignant nodules and discontinuing contour of the lesion thyroid outline and vague fatty space around thyroid were shown.Trachea of 4 patients with thyroid carcinoma and carotid sheath of 6 patients and tracheo-asophageal colpus of 4 patients and neck muscles and connective tissue of 9 cases were invaded by malignant lesions.The ipsilateral enlarged lymph nodules were found in 7 patients with thyroid carcinoma.The CT diagnostic accuracy of benign thyroid nodules was 84.6%.In 12 patients with benign thyroid nodule,clear contour and intact thyroid outline were shown and clear fatty space could also be seen.The total CT diagnostic accuracy of all 27 patients with benign and malignant thyroid nodules was 88.9%.Conclusions: Thin slice enhanced CT scan can play an important role in differential diagnosis of thyroid nodules.