Aim of the study: This study aims to examine how many radioiodine ablations were applied in one year, the number of high-risk and low-risk patients, and their characteristics (age, gender); whether there is a difference in tumor marker levels before and after ablation therapy for high-risk and low-risk patients; and the effect of ablation on the scintigram findings at the first major control. Study design: The research was conducted as a cross-sectional study with historical data. Materials and methods: The study included patients of both genders and all age groups who were diagnosed with thyroid cancer and were treated at the Clinical Institute for Nuclear Medicine and Radiation Protection of KBC Osijek in the period from January 1, 2020 to December 31, 2021. The data was collected using BIS, and then analyzed and statistically processed. Results: In one year, 39 radioiodine ablations were applied. Out of the total number of patients, which is 39, 17 patients belong to the high-risk group, and 22 patients to the low-risk group. Considering the representation by gender, there were a total of 30 women and 9 men. The median age of all patients was 54 years. The value of the tumor marker Tg decreased significantly after ablation therapy. Also, both groups, high-risk and low-risk, showed a decrease in Tg values, while anti-Tg values did not decrease. Ablation therapy showed a positive effect on scintigram findings at the first major control, and out of a total of 39 patients, even 29 had scintigram findings without pathological accumulation of I-131 activity. Conclusion: The study has shown a positive effect of ablation therapy with iodine 131 on scintigram findings at the first major control, and on the values of the thyroid cancer tumor marker thyroglobulin in all patients, as well as in high-risk and low-risk groups of patients individually.