Aim. To determine the diagnostic value of endosonography in primary and secondary esophageal tumors. Materials and methods. Between 2018 and 2022, 118 patients with primary and secondary esophageal changes were managed at the Blokhin National Medical Research Center for Oncology. Primary changes imply invasion of the esophagus directly by a tumor, secondary changes mean invasion of the esophageal wall by a tumor from outside, and the transition of a tumor from the stomach to the esophagus. Results. All patients had esophagogastroduodenoscopy combined with endoscopic ultrasound performed. Besides estimating the tumor invasion depth in the esophageal wall and the possible involvement of other structures at a distance up to 5 cm from the esophagus, the proximal margin of the tumor was examined. According to esophagogastroduodenoscopy and endoscopic ultrasound examination, the difference in the proximal margin was not more than 1.0 cm. The difference in results may be due to the submucosal nature of tumor growth. Conclusion. Endoscopic ultrasound examination is the most important diagnostic method to determine the proximal margin of the primary and secondary esophageal tumors and evaluate the degree of invasion into the esophageal wall, which is an essential factor for the treatment choice.