Fine needle aspiration biopsy (FNAB) is the gold standard for the diagnosis of lymphoma in Hashimoto's thyroiditis and is able to differentiate between benign, inflammatory or malignant nodules, classifying them as either true nodules or pseudonodules. This technique is, however, invasive. The present study aimed to differentiate pseudonodules from true nodules by sonoelastography, a non-invasive technique, in 54 patients with Hashimoto's thyroiditis. The accuracy of sonoelastography to differentiate between true or pseudonodules was compared with the gold standard FNAB and with grey scale ultrasonography. The nodules were categorized into three groups: non-demarcated hypoechogenic, demarcated hyperechogenic, and demarcated hypoechogenic. Sonoelastography findings were concordant with the cytopathological results and demonstrated that sonoelastography was able to detect true thyroid nodules often misdiagnosed by conventional grey scale ultrasonography. Sonoelastography was found to have increased sensitivity for true nodule diagnosis compared with conventional grey scale ultrasonography and may eliminate unnecessary FNABs being carried out.