Background. GastroEsophageal Reflux Disease (GERD) is a common problem among obese and overweight people, including as a complication of bariatric surgery, Laparoscopic Sleeve Gastrectomy (LSG). Aim. To conduct a retrospective analysis of the frequency of GERD in patients with morbid obesity after laparoscopic sleeve gastrectomy. Materials and Methods. In this retrospective study, data from 152 patients who underwent LSG were analyzed. All patients were diagnosed with morbid obesity and were deemed suitable for surgery. The minimum follow-up period was twelve months. All patients were assessed preoperatively for the severity of GERD using 24-hour pH monitoring, and upper gastrointestinal tract examination via FibroGastroDuodenoScopy (FGDS) to identify signs of reflux disease, esophagitis and Barrett's esophagus and GERD-HRQL (Health-Related Quality of Life) questionnaire. Results. During the study, out of 152 patients without GERD (DeMeester Index (DMI) was 6.87±3.38), 23 (15.1%) of them within 12 months after LSG developed de novo GERD (DMI 9.12±8.87, p=0.04). In four patients with de novo GERD, esophagitis grade A was detected. The pathomechanism of GERD following LSG was multifactorial, caused by a combination of anatomical, physiological, and physical factors. Contributing factors included the shape of the sleeve, damage to the lower esophageal sphincter, and esophageal motility disorders. Conclusions. LSG is effective in promoting weight loss, but poses a significant risk of developing GERD. Our study found a 15.1% incidence of GERD after LRH, which is lower than other studies, probably due to the routine use of 24-hour pH monitoring to identify patients with asymptomatic GERD. Anatomical changes due to LSG, in particular resection of the gastric fundus and dissection in the area of the angle of His, increase the temporary relaxation of the lower esophageal sphincter, contributing to the development of GERD. Keywords: bariatric surgery, morbid obesity, GERD.