We assessed whether the laparoscopic hyperthermic intraperitoneal chemotherapy (L-HIPEC) + neoadjuvant intraperitoneal and systemic chemotherapy (NIPS) could reduce the peritoneal cancer index (PCI; which is defined by Sugerbaker) and improve the possibility to obtain a complete cytoreductive surgery (CRS with peritonectomy; basically according to the Sugerbaker's procedure). After L-HIPEC + NIPS, the PCI score was decreased in 89.5 per cent of patients, and the average score was significantly reduced. The average PCI reduction of improved PCI cases was 10.2 ± 8.4. The hypothetical cut-off was at a PCI score of six with significant higher possibility of CRS completeness. Twelve patients had high-PCI (PCI > 6), and six of them (50.0%) were converted to low-PCI (PCI ≦ 6) and got a complete CRS. There was a significant relationship between post-PCI (PCI after L-HIPEC + NIPS) and CRS completeness; however, pre-PCI (PCI before L-HIPEC + NIPS) value was not a relevant factor. The high-PCI and increased PCI even after L-HIPEC + NIPS (deteriorated-PCI) were suggested as important risk factors for surgical completeness. Neither pre- nor postcytological results had a significant relationship between CRS completeness. However, the deteriorated cytological class was considered as a risk factor for CRS completeness. The second-look laparoscopy would be recommended for the better selection of the patients who can receive benefits by this extensive surgery.