| Summary: | (1) Background: The aim of our study is to reveal the advantages and limitations of the use of <sup>99m</sup>TcEDDA/HYNIC-TOC (Tektrotyd<sup>®</sup>, Polatom) in the diagnosis of gastroenteropancreatic neuroendocrine tumors and to compare our results with the values obtained for <sup>111</sup>In-pentetreotide and <sup>68</sup>Ga-DOTA-peptides, routinely used in medical practice. (2) Methods: This retrospective monocentric study included 173 patients with gastroenteropancreatic neuroendocrine tumors who underwent <sup>99m</sup>TcEDDA/HYNIC-TOC scans as part of their clinical management. The examination protocol included a whole-body scan acquired 2 h after the radiotracer’s administration, with the SPECT/CT performed 4 h post-injection. Physiological and abnormal uptake were established by two experienced physicians and, based on the obtained results, sensitivity, specificity, accuracy, positive predictive value and negative predictive value were calculated. (3) Results: Our method presented a sensitivity of 90.5%, a specificity of 71.9%, and an accuracy of 84.3%, with a positive predictive value of 86.7% and a negative predictive value of 78.8%. (4) Conclusions: <sup>99m</sup>Tc-EDDA/HYNIC-TOC, a receptor-based radiopharmaceutical, could represent a competitor for <sup>68</sup>Ga-labeled peptides in the diagnosis and management of patients with gastroenteropancreatic neuroendocrine tumors. Our results show a lower sensitivity (90.5%) than <sup>68</sup>Ga-DOTA-peptides, but with great specificity, accuracy, positive, and negative predictive values.
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