Introduction One of the most recent techniques in imaging tumors is the diffusion-weighted MRI. It provides information regarding the metabolic, molecular, and pathophysiological aspects of tumors, especially thyroid gland cancer. Diffusion-weighted imaging (DWI) has also been proposed as a sensitive marker for monitoring treatment response in head and neck cancers. The biophysical mechanism of DWI is based on the translational motion of water molecules in tissues. The magnitude of this motion is characterized by its apparent diffusion coefficient (ADC) values. Objective The aim of the present study was to evaluate the certainty of ADC value in differentiating between benign and malignant thyroid lesions. Materials and methods Neck MRI with several sequences including DWI in the axial plane were carried out for 49 patients who presented with thyroid masses either benign or malignant. ADC maps were calculated by using the MRI machine software. Results A total of 49 patients (77.6%) were included in the present study. There were 11 men (22.4%) and 38 women patients (77.6%), with a mean age of 44.4 years. The lesions were benign in 31 cases (63.3%) and malignant in 18 cases (36.7%). The ADC values were significantly different (P<0.001) between benign and malignant lesions. Conclusion ADC value is a promising noninvasive imaging tool that can be used for characterization and differentiation of thyroid nodules.