Elastography is a method of tissue stiffness assessment. It has already been demonstrated that thyroid cancers are less elastic than benign lesions. However, little is known about other factors, which might influence the stiffness of thyroid nodules and disrupt the prediction of malignancy using this technique. The aim of this study was to conduct the first systematic assessment of factors potentially affecting the elasticity of thyroid lesions. One hundred and twenty-two patients with thyroid nodular disease admitted for thyroidectomy underwent preoperative ultrasonography and sonoelastography. The definite diagnosis of thyroid lesions was based on histological examination. What was evaluated in the study was the influence of composition, size, localization, nodularity, and selected laboratory parameters on thyroid nodule elasticity. Firstly, association between the above-mentioned factors and elasticity was assessed in benign lesions. Secondly, all nodules (benign and malignant) were divided into subgroups according to the presence or absence of particular features, which turned out to be an important disturbing factor increasing the stiffness of the lesion in the first step of analysis. There were 22 malignant and 371 benign lesions. The analysis of benign lesions revealed that the presence calcifications (p < 0.0001) significantly increased nodule stiffness. Partially, cystic nodules were significantly less elastic than solid ones (p = 0.03). There was also positive correlation between nodule size and stiffness (p < 0.0001). Lesions localized in the isthmus were significantly less elastic than nodules in other localizations. (p = 0.0001). Solitary nodules were less elastic than lesions in multinodular goiter (p = 0.006). Correlation between Tg concentration and stiffness was significant (p < 0.0001, r = 0.24). The concentration of anti-thyroid autoantibodies was associated with stiffness at the border of significance. However, there was no significant difference between benign lesions in patients with diagnosed chronic autoimmune thyroiditis and patients without the disease. The analysis of the entire group of nodules revealed that shear wave elastography is a valuable modality of thyroid nodule assessment, with sensitivity of over 95 % and specificity of about 70 %. However, the stiffness value of the lesion might be increased in the case of nodules containing calcifications, cystic component, and those of size above 20 mm. Certain clinical conditions or attributes of the lesions influence the stiffness values of thyroid nodules. Identifying these variables is the basis for a credible interpretation of the results of a sonoelastographic examination and makes it possible to estimate the risk of thyroid nodule malignancy adequately.