Abstract: Studies on whether the brain of internet addicts are different from the normal users’ would contribute to defining, diagnosis and treatment of internet addiction. In recent years, cognitive neuroscience studies have suggested that, compared with normal users, internet addicts’ brain have four main abnormalities: a. frontal lobe and cingulated gyrus are atrophic and degradative, resulting in inability to control their internet use. b. Hippocampus is dysfunctional, resulting in the decline of cognitive ability, especially working memory. c. Compensation of the reward center is enhanced, which is probably related to dysfunction of dopaminergic system. d. Posterior limb of internal capsule of people with internet addiction becomes more dense and active, which may be related to the fact that IAD subjects spent too much time on computer games and their repetitive actions such as mouse clicking and keyboard typing. These studies, at least, indicate that there are abnormalities in function of addicts’ brain, which are similar to substance addicts’. However, further researches are still needed to make sure whether these abnormalities are caused by internet addiction and whether these abnormalities are structural or chronic.

Key words: Internet Addiction, brain structure, brain function, abnormality