Introduction: Adnexal masses are a common finding in gynecological sonographic examinations. Usually, these tumors are detected in early stages while they are asymptomatic. However, in some cases ovarian masses remain undetected and grow to giant size. The majority of these giant tumors are benign. Here we report two cases of giant ovarian mucinous tumors with areas of borderline malignancy. Case description: We present the cases of two women, aged 45 and 54 years, with abdominal masses causing vague symptoms. Abdominal imaging revealed giant cystic masses arising from the pelvis. Both women treated surgically. The first woman underwent right adnexectomy and the second one a total hysterectomy with bilateral adnexectomy and omentectomy. In both cases, the histopathological diagnosis was giant ovarian mucinous borderline cystadenoma. On the 12-month follow up they do not report any discomfort. Discussion and conclusion: Giant ovarian mucinous borderline tumors are uncommon and need surgical resection to eliminate the compressive symptoms that they usually cause. A giant abdominal mass must be always suspected in women with vague compressive symptoms. [ABSTRACT FROM AUTHOR]