This short review aims at summarizing the available data pertaining to the usefulness of F-18 FDG PET/CT in rectal cancer. It is specifically focused on the emerging role of F-18 FDG PET/CT in assessing the response to neoadjuvant combined radiochemotherapy in locally advanced rectal cancer. It also probes the possibility of finding standardized PET/CT parameters that are capable of differentiating responders from nonresponders in whom therapeutic approach could be modified.