Background:To evaluate functional visceral adipose tissue (VAT) activity assessed by18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) as a predictive factor of metastases in colorectal cancer (CRC) patients.Methods:We reviewed study protocols and PET/CT data of 534 CRC patients; 474 patients were subsequently excluded for various reasons. The remaining 60 patients with histologically confirmed adenocarcinoma were then prospectively assessed and were exposed to18F-FDG PET/CT after a surgical treatment and chemoradiotherapy. Age, histology, stage, and tumor grade data were recorded. Functional VAT activity was verified with maximum standardized uptake value (SUVmax) using18F-FDG PET/CT and tested as a predictive factor of later metastases in eight subdomains of abdominal regions (RE – epigastric region, RLH – left hypochondriac region, RRL – right lumbar region, RU – umbilical region, RLL – left lumbar region, RRI – right inguinal region, RP – hypogastric (pubic) region, RLI – left inguinal region) and pelvic cavity (P) in the adjusted regression models. In addition, we studied the best areas under the curve (AUC) for SUVmaxwith the corresponding sensitivity (Se) and specificity (Sp).Results:In both adjusted for age regression models and receiver operating characteristic (ROC) curve analysis,18F-FDG accumulation in RLH (cut-off SUVmax0.74; Se 75%; Sp 61%; AUC 0.668; p=0.049), RU (cut-off SUVmax0.78; Se 69%; Sp 61%; AUC 0.679; p=0.035), RRL (cut-off SUVmax1.05; Se 69%; Sp 77%; AUC 0.682; p=0.032) and RRI (cut-off SUVmax0.85; Se 63%; Sp 61%; AUC 0.672; p=0.043) could predict later metastases in CRC patients, as opposed to age, sex, primary tumor location, tumor grade and histology.Conclusions:Functional VAT activity was importantly related to later metastases in CRC patients and can be used as their predictive factor.