  Modifications of jets in the existence of a hot and dense QCD medium have
recently attracted a lot of attentions. In this talk, we demonstrate how
jet-medium interactions change the behavior of jets by offering examples of
inclusive jet and dijet productions at $ {\cal O}(\alpha_s^3)$ in heavy ion
collisions including initial-state cold nuclear effects and especially the
final-state parton energy loss effect. The suppression of inclusive jet
spectrum varying with jet radii and a flatter dijet momentum imbalance as
compared to those in hadron-hadron collisions are observed in high-energy
nuclear collisions.
