Gastrointestinal stromal tumors (GIST) are the most common mesenchymal neoplasms of the gastrointestinal tract with a malignant potential. However, uncommonly they can be associated with synchronous tumors of different histogenesis. We herein report two cases of gastric GIST with synchronous tumors. The first case is of a 50-year-old male patient who was suspected with GIST of stomach and was incidentally found to have an associated duodenal neuroendo-crine neoplasm. The second case is of a 62-year-old male who, while undergoing surgery for a primary colon adenocarcinoma, was incidentally detected to have a coexistent gastric GIST initially suspected to be a metastatic nodule. Coexistence of gastric GIST with neuroendocrine tumor is extremely rare. To the best of our knowledge this is the second case of gastric GIST coexisting with duodenal neuroendocrine tumor to be reported in the literature. Similarly, association of GIST with adenocarcinoma is uncommon. We herein analyze the pathological findings of two such cases, and we review the malignant potential of these synchronous tumors.