The simultaneous occurrence of different types of thyroid carcinoma in a single patient is very rare. We report a case of synchronous occurrence of medullary thyroid carcinoma and papillary thyroid carcinoma, presenting as spatially distinct and well-defined tumour components. A 52-year-old woman was referred to our hospital for evaluation of palpable thyroid mass. In the ultrasonography, there were a malignant looking 2.1x2.4x2.8 sized mass in right lobe and another malignant looking 0.28x0.33x0.38cm sized nodule in left lobe. Fine-needle aspiration (FNA) cytology revealed suspicious papillary carcinoma in the left lobe and atypical cells of undetermined significance in the right lobe. She received total thyroidectomy. Pathological examination showed a 2.9 cm medullary carcinoma in the right lobe as well as a 0.2, 0.1, 0.1cm sized multifocal papillary carcinoma in the left lobe. All tumors were clearly separated from each other, representing the pure entity of each type. Until now, synchronous occurrence of papillary and medullary thyroid carcinoma is rarely reported and also there is no known common cause and clinical prognosis of these different tumor types. Further studies including molecular analysis will be needed to evaluate underlying pathogenesis of this case.