Ovarian fibrothecoma is a rare, benign neoplasm of the sex cords and stroma of the ovary. Patients may present with abdominal pelvic pain and / or distension, and sometimes postmenopausal bleeding. Large tumors (> 10cm) are often associated with pleural and peritoneal effusion mimicking an advanced ovarian malignancy (Deimon â€“Meigs syndrome). We report 2 cases of giant fibrothecoma associated with ascites and pleurisy. Both patients were postmenopausal. The ovarian tumor was discovered during an increase in abdominal volume in the first patient and as part of the etiological workup of encysted pleurisy in the second. The clinical examination made it possible to objectify a tumor with abdominopelvic development of size greater than 10 cm, the clinical examination also noted, in the two patients, a right basithoracic dullness in favor of a pleurisy and an ascites of average abundance suggesting in the first place a malignant tumor of the ovary, with peritoneal carcinoma. the two patients underwent a pelvic ultrasound, supplemented by an abdominal pelvic CT scan objectifying the presence of a large ovarian mass with pleural and peritoneal effusions. Exploratory laparotomy was required in both patients and underwent an extemporaneous examination which was consistent with the definitive pathological examination in both patients. Both patients underwent total hysterectomy with bilateral adnexectomy and omentectomy with multiple biopsies as the clinical picture was highly suggestive of malignancy. The postoperative follow-up was simple with total regression of peritoneal and pleural effusions in the two cases of Demons-Meigs syndrome. The definitive pathological examination revealed a fibrothecoma. Fibrothecal tumors remain a real challenge from a diagnostic and therapeutic point of view. The fear of cancer is even greater in the presence of Demons-Meigs syndrome. The management of these tumors requires a good clinical and radiological analysis, and it is the histological examination that confirms the diagnosis. The surgery corresponds, in post-menopausal patients, to a hysterectomy with bilateral adnexectomy, while conservative treatment by unilateral adnexectomy is entirely justified in young women who still want fertility.