Intrathyroidal paragangliomas are very rare tumours. We report a case of a 32 year-old woman with a mass in the right lobe of the thyroid gland, without other symptoms. The first diagnosis was a thyroid medullary carcinoma, after fine-needle aspiration. The therapeutical option was right hemithyroidectomy. Histological pattern and immunohistochemical study were compatible with paraganglioma. We emphasise the diagnostic difficulties and the importance of immunohistochemical markers