Objective: To analyze ¹⁸F-fluorodeoxyglucose(FDG) PET/CT imaging manifestations in patients with peritoneal carcinomatosis (PC) from colorectal cancer (CRC) and investigate its clinical significance. Methods: From May 2016 to August 2018, 46 patients (25 males, 21 females; age range: 36-82(62.0±10.4) years) with PC from CRC who underwent ¹⁸F-FDG PET/CT imaging in Affiliated Hospital of Nantong University and had complete clinical data were retrospectively analyzed. The peritoneal carcinomatosis index (PCI) grading system was used to evaluate the PC lesions. Independent-sample t test and Kruskal-Wallis H test were used for data analysis. Results: There were various CT manifestations of PC, while FDG metabolism on PET was observed in all 46 patients. Patients were divided into different groups according to the location of the primary CRC lesion. The diameter of PC lesion in the left colon group was (2.46±1.26) cm, which was significantly different from that of the rectum group ((3.19±1.72) cm; t=-2.77, P<0.01). The maximum standardized uptake value (SUV_max) in the right colon group were significantly higher than that in the left colon group (9.16±4.79 vs 6.99±3.50; t=2.92, P<0.01). The PCI score ranged from 1 to 30 in 46 patients, and there was no significant difference in PCI score distribution (≥20 vs <20) among the right colon group, left colon group and rectum group (H=0.242, P>0.05). Ten patients had abdominal and pelvic effusion. Conclusion ¹⁸F-FDG PET/CT can well display the PC in patients with CRC, and the combination of PCI and ¹⁸F-FDG PET/CT plays an important role in the diagnosis and treatment of PC.