Addiction to illicit drugs is one of today's most important social issues. Most addictive drugs lead to irreversible parenchymal changes in the human brain. Neuroimaging data bring to light the pharmacodynamics and pharmacokinetics of the abused drugs, and demonstrate that addiction is a disease of the brain. Continuous researches better illustrate the neurochemical alterations in brain function, and attempt to discover the links to consequent behavioral changes. Newer hypotheses and theories follow the numerous results, and more rational methods of approaching therapy are being developed. Substance abuse is on the rise in Korea, and social interest in the matter as well. On the other hand, diagnosis and treatment of drug addiction is still very difficult, because how the abused substance acts in the brain, or how it leads to behavioral problems is not widely known. Therefore, understanding the mechanism of drug addiction can improve the process of diagnosing addict patients, planning therapy, and predicting the prognosis. Neuroimaging approaches by nuclear medicine methods are expected to objectively judge behavioral and neurochemical changes, and response to treatment. In addition, as genes ssociated with addictive behavior are discovered, functional nuclear medicine images will aid in the assessment of individuals. Reviewing published literature on neuroimaging regarding nuclear medicine is expected to be of assistance to the management of drug addict patients. What's more, means of applying nuclear medicine to the care of drug addict patients should be investigated further. (Nucl Med Mol Imaging 2006;40(1):1-8)