Parathyroid carcinoma is rare disease representing 1% to 4% of the cases of hyperparathyroidism. Coincidence of thyroid carcinoma in parathyroid adenoma is not uncommon, but synchronous parathyroid and thyroid carcinoma is extremely rare. As far as our investigation permits, there are only 4 cases reported in the literature of the world. Recently we experienced 2 cases of synchronous parathyroid carcinoma and papillary thyroid carcinoma. Both conditions developed in non-irradiated neck. The first case was preoperatively diagnosed as papillary carcinoma with nodal involvement, and the second, which presented the symptoms of hyperparathyroidism, was diagnosed as primary hyperparathyroidism combined with benign thyroid nodule preoperatively. Both cases, however, turned out to be coexisting parathyroid and papillary thyroid carcinomas. Surgeons should be aware of this condition when encountered with thyroid and parathyroid tumor in a patient.