Abstract: PET-CT using ¹⁸F-FDG is a non-invasive imaging modality which has been recognized as the most important imaging modality in diagnosing, staging, restaging, therapy monitoring and follow-up of cancer patients, especially in metastatic colorectal cancer.PET-CT combines functional and anatomical imaging to improve sensitivity and specificity of whole-body imaging and provides incremental diagnostic value over PET or CT alone.Nowadays, applications of PET-CT imaging in liver metastasis from colorectal cancer mainly included detection and differentiation of malignant and benign liver lesions, determination of appropriate therapeutic strategies and evaluation of treatments.