The aim of the article was to study morphological features of esophageal mucosa in patients with type II diabetes mellitus and gastroesophageal reflux disease (GERD). The research was conducted on 67 patients with type II diabetes mellitus and GERD and 50 non-diabetic patients with GERD. The histological study of the mucous membrane of the distal esophagus in patients with combined pathology detected parakeratosis and acanthosis, outflows edema and bundles epithelium, surfacial hyperplasia, infiltration of neutrophils and vascular ectasia. The obtained results demonstrate that type II diabetes causes change in symptoms, endoscopic and histologic manifestations of GERD. It is concluded about the importance to develop and improve diagnostic tools for the detection of GERD with type II diabetes by means of invasive and non-invasive diagnostic techniques.