Retroperitoneal cystic masses can be benign or malignant, purely cystic or with solid components. Several diagnoses can be evoked in front of a retroperitoneal cystic mass among which: the hydatid cyst of the psoas. The hydatid cyst of the psoas constitutes an exceptional localization of hydatidosis, even in hydatid endemic countries such as Morocco where hydatidosis remains frequent. We report 2 cases of hydatid cyst of the psoas, collected in the department of visceral surgery B at the CHU Ibn Sina in Rabat during a period of 5 years. Our objective was to focus on the diagnostic and therapeutic difficulties of this condition. The clinical symptomatology consists of lateralized pain or at the level of the iliac fossa, it can be associated with an infectious syndrome which directs towards an abscess of the psoas but most often the evolution is done in a context of apyrexia and conservation general condition. The thoraco-abdominal CT confirmed the diagnosis and made it possible to specify the seat of the cyst and its neighborhood relationships. Therapeutic management was surgical in all cases; the diagnosis was made intraoperatively. The technique used was resection of the protruding dome via the midline, sub umbilical abdominal route for the first patient and pericystectomy via the Jalaguier approach for the second patient. The postoperative course was favorable in both cases and no case of recurrence was reported in our series.