Adenocarcinomas of the esophagogastric junction (AEG) are now recognized as a separate tumor entity with increasing incidence. The aim of the present study was to evaluate whether positron emission tomography (PET) using the glucose analog F-18-fluorodeoxyglucose (FDG) can be used for metabolic characterization of this tumor type. Fifty-two patients with histologically proven, locally advanced AEG (distal esophagus, type I: n = 31; cardia, type II: n = 21) were studied by FDG-PET. None of the tumors had been previously treated. Findings of endoscopy (growth type), endoluminal ultrasound (uT, uN), computed tomography (cN, cranio-caudal extent, tumor thickness), histological evaluation (Lauren classification, tumor grade), anatomical classification, and survival were correlated with the results of FDG-PET. There was no correlation between FDG uptake and clinical stage, grade, Lauren classification, or survival. All AEG I tumors were visualized by FDG-PET with high contrast, whereas FDG uptake by five AEG II tumors (24%) did not differ from background activity. In a quantitative analysis, mean FDG uptake of AEG I tumors was 1.6 times higher than that of AEG II tumors ( p = 0.0005). PET can be used to visualize type I adenocarcinomas of the esophagogastric junction (AEG I). In AEG II tumors, however, the use of FDG-PET appears to be limited. The significantly higher FDG uptake of AEG I tumors compared to AEG II tumors suggests that these two tumor types differ in glucose utilization. This finding strengthens the hypothesis that AEG I and AEG II are two different tumor entities.