Peritoneal carcinomatosis and peritoneal sarcomatosis in children are rare and might occur in colorectal cancer, desmoplastic small round cell tumors (DSRCT), rhabdomyosarcoma, and other entities. The treatment of these children is still a major challenge as despite very intensive therapies consisting of systemic chemotherapy, radiotherapy, and surgery, outcomes have not been improved significantly. Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) have now been implemented in the treatment of these children and show promising first treatment results. The chapter summarizes special technical aspects of these procedures in children and sums up actual treatment results.