Purpose : To decrease the risk of recurrence or metastasis in differentiated thyroid cancer (DTC), selected patients receive radioactive iodine ablation of remnant thyroid tissue or tumor. A low iodine diet can enhance uptake of radioactive iodine. We compared the success rates of radioactive iodine ablation therapy in patients who followed two different low iodine diets (LIDs). Materials and Methods : The success rates of postsurgical radioactive iodine ablation in DTC patients receiving empiric doses of 150 mCi were retrospectively reviewed. First-time radioactive iodine ablation therapy was done in 71 patients following less strict LID and 90 patients following very strict LID. Less strict LID restricted seafood, iodized salt, egg yolk, dairy products, processed meat, instant prepared meals, and multi-vitamins. Very strict LID additionally restricted rice, freshwater fish, spinach, and soybean products. Radioactive iodine ablation therapy was considered successful when follow-up $^{123}I$ whole body scan was negative and stimulated serum thyroglobulin level was less than 2.0 ng/mL. Results : The success rate of patients following less strict LID was 80.3% and for very strict LID 75.6%. There was no statistically significant difference in the success rates between the two LID groups (p=0.48). Conclusions : Very strict LID may not contribute to improving the success rate of initial radioactive iodine ablation therapy at the cost of great inconvenience to the patient.