Radioiodine therapy for benign and malignant thyroid diseases was introduced about 70 years ago, however, there is still a lack of consensus regarding indications, doses and procedure. This review covers treatment results in immunogenic hyperthyroidism including the problem of orbitopathy. Radioiodine therapy for toxic and non-toxic multinodular goiter is also discussed with striking possibility of enhanching the radioiodine uptake. In this respect the recombinant human thyrotropin should be mentioned. Thyroid cancer treatment protocol has changed, too, due to ineffectivity in low-risk patients. More attention is needed to the carcinogenecity of radioiodine. The numerous problems mentioned above require large and well-designed prospective trials to resolve the fundamental questions. The author emphasizes that radioiodine dose should be administered in doses as low as reasonably achievable.