Hashimoto's thyroiditis (HT) is considered as one of the most common immunological disorders influencing the thyroid gland. This disorder affect mostly the middle aged people especially the female inspite that there is no age group exclusion. It is a common cause of hypothyroidism. It was clearly that HT is correlated with thyroid cancers especially papillary thyroid carcinoma and lymphoma. In this article we tried to focus the main points of immunopatho- genesis, differential diagnosis and cancer association.