Gastrointestinal stromal tumors (GISTs) are common mesenchymal tumors of the digestive tract. These tumors occasionally present a pelvic mass and leading to the misdiagnosis of gynecologic diseases. Two patients with GIST in the small intestine giving an impression of an ovarian fibroma and a uterine leiomyoma respectively were diagnosed correctly at the surgery. In the patients with a pelvic mass, especially if unusual symptoms and laboratory data being not compatible with gynecological disease, the possibility of diseases other than a gynecologic disease has to be considered.