Background In this study, we aimed to evaluate ultrasonographical and cytological features of thyroid nodules in patients who were treated with radioactive iodine (RAI) for hyperthyroidism years ago. Methods Patients who had a history of RAI treatment for hyperthyroidism and had thyroid nodules that were evaluated with fine-needle aspiration biopsy (FNAB) were included in the study. Results There were 27 patients (22 female and 5 male) with a mean age of 59.3 +/- 13.5. The indication for RAI treatment was Graves in 5 (18.6%), toxic nodular or multinodular goiter in 16 (69.2%), and unknown in 6 (22.2%) patients. A total of 48 thyroid nodules were evaluated with FNAB and cytological diagnosis were benign in 24 (50.0%), nondiagnostic in 15 (31.2%), atypia of undetermined significance in 5 (10.4%), suspicous for malignancy in 2 (4.2%), and malignant in 2 (4.2%) nodules. Thyroidectomy was performed in 10 patients, 5 were benign (50.0%), and 5 (50.0%) were malignant histopathologically. Ultrasonography features of 31 cytologically/histopathologically benign and five cytologically/histopathologically malignant nodules were compared. Prevalence of isoechoic nodules was higher in benign nodules (P = .025). Macrocalcification was observed in 4 (80.0%) of malignant and 10 (32.3%) of benign nodules (P = .042). Conclusion In patients with a history of RAI treatment for hyperthyroidism, thyroid nodules with suspicious ultrasonography features, particulary hypoechoic appearence and macrocalcification, should be evaluated with FNAB irrespective of the time elapsed after RAI treatment.