In a group of 209 colorectal cancer patients with unresectable tumors, 10 patients underwent curative resection after combination chemotherapy at our hospital between 2006 and 2012. Of these 10 patients, 5 presented with peritoneal dissemination at the start of chemotherapy. With the exception of 1 patient with peritoneal recurrence, peritoneal dissemination and liver metastasis were observed in all patients at the time of diagnosis of colorectal cancer. Computed tomography (CT) and/ or positron emission tomography-CT examination revealed disappearance of peritoneal dissemination in response to chemotherapy, except in 1 patient with peritoneal recurrence. After combination chemotherapy, surgical resection of liver metastases and peritoneal dissemination was performed. Pathological and intraoperative findings indicated disappearance of peritoneal dissemination in 3 patients and P2 grade peritoneal dissemination in 1 patient. In the patient with peritoneal recurrence, 1 tumor was completely resected. Interestingly, none of the 3 patients that exhibited complete disappearance of peritoneal dissemination showed peritoneal recurrence, although 1 patient exhibited metastases in the lung and non-regional lymph nodes. In contrast, the patient with P2 grade peritoneal dissemination showed peritoneal recurrence and lung metastasis. All 5 patients survived (duration from diagnosis of colorectal cancer, 31-83 months). Herein, we report the use of combination chemotherapy to achieve the disappearance of peritoneal dissemination, changing unresectable colorectal cancer with peritoneal dissemination into resectable cancer.