Recent studies reported the role of several trace elements in health and disease. The role of iodine deficiency in thyroid dysfunction is well known. Also the selenium deficiency has been reported to be correlated to thyroid dysfunctions. In fact, although the major role of selenium is related to the glutathione peroxidase system, which protects cellular structures from oxidative damages, selenium plays also an important role in thyroid hormone metabolism as an essential component of the three deiodinase. These regulate inter-conversion of active and inactive forms of iodothyronines. Several studies have been carried out to establish the role of combined selenium and iodine deficiency. This review aims to provide information on the relationship between selenium and iodine intake and thyroid function. Furthermore, the state of art on the effects of the combined deficiency of selenium and iodine is also provided.