Abstract: Objective To investigate the value of detecting cytokeratin 19(CK19) and thyroperoxidase (TPO) expression in the diagnosis of thyroid diseases including thyroid carcinoma, multinodular goiter, adenoma and Hashimoto thyroiditis. Methods SP immunohistochemistry was used to detect the expressions of CK19 and TPO in paraffin-embedded thyroid tissue specimens obtained from 62 patients with thyroid carcinoma (30 with papillary carcinomas, 22 with follicular variant of papillary carcinomas, and 10 with follicular carcinomas) and 44 with benign thyroid diseases (including 22 with multinodular goiters, 14 with adenoma, and 8 with Hashimoto thyroiditis). Results CK19 expression was detected in 96.8% of the thyroid carcinomas and in 4.5% of benign thyroid diseases, demonstrating a significant difference in CK19 expression between the two thyroid diseases (P<0.01). TPO expression was found in 100% of benign thyroid disease and in 3.2% of thyroid carcinoma, showing also a significant difference between them (P<0.01). Conclusion CK19 and TPO can be important molecular markers for diagnosing thyroid carcinoma.