The primary malignant tumor of the peritoneum also known as primary peritoneal carcinoma or primary peritoneal papillary serous carcinoma is rare and involves the peritoneum, especially the pelvic peritoneum of female patients. It is difficult to differentiate histologically between papillary mesothelioma, primary ovarian tumor and primary peritoneal carcinoma. We report two cases of the primary peritoneal carcinoma with clinical presentation and histologic characteristics.