Objectives The aim of this study is to evaluate the diagnostic value of neck ultrasound during follow-up of patients with DTC. The following diagnostic features were determined; sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV). Study Design A cross-sectional study. Patients and Methods The research includes 388 patients with DTC. All patients were exposed to total thyroidectomy and ablation radioiodine therapy with I – 131. Follow – up of thyroid DTC included periodic measurement of sTg concentration (basal and stimulating thyroglobulin), diagnostic scintigraphy of the whole body with I – 131, and ultrasound of the neck, with ev. cytological puncture. The value of diagnostic tests after one year and after three years was analyzed. Results With diagnostic tests, the highest percentage of relapses was detected by determining sTg (90,7 %), while a positive finding was present in 27 patients (81,8 %) using USG. After the first major check – up, only 4 patients had a false negative sTg, and it is important to emphasize that neck ultrasound with cytological puncture and additional imaging tests (CT and bone scintigraphy) played a crucial role in the detection of these recurrences. Conclusions The high sensitivity of neck ultrasound with CP (81,8 %) was confirmed as a basic test in the detection of structural recurrences of the neck during the follow – up of patients with DTC. The study showed that a large proportion with a proper first "big" check – up can be well monitored SUMMARY 20 and treated without repeated sTg measurements and exposure to scintigraphy of the whole body with I – 131. The majority of such patients need to be regularly monitored with neck ultrasound and sTg measurements in conditions without TSH stimulation.