Converging evidence from clinical, animal, and neuroimaging experiments suggests that the addictive behavior is associated with dysregulated dopamine neurotransmission. The precise role of dopamine in establishment and maintenance of addiction however is unclear. In this context animal studies on the brain reward system and the associative memory processing provide a novel insight. It was shown that both processing involve dopamine neurotransmission and both are disrupted in addiction. These findings indicate that dysregulated dopamine neurotransmission alters the brain processing of not only the reward system but also that of the memory of association between an addictive substance and reward. These alterations lead to maladaptive motivational behavior leading to chemical dependency. This concept however is based mostly on the data obtained in laboratory animals because of the paucity of human data. Due to lack of a reliable technique to study neurotransmission in the live human brain, it has been a problem to study the role of dopamine in human volunteers. A recently developed dynamic molecular imaging technique however, provides an opportunity to study these concepts in human volunteers because the technique allows detection, mapping and measurement of dopamine released in the live human brain during task performance.