Attention is a phenomenon hard to define, but can be conceptualized as a mental function ranging from sustaining readiness to perceive stimuli to understanding the nature and value and selecting stimuli that are most relevant to the given situation. Manifestations of attention include vigilance, and focused, directed, selective, divided, and sustained attentions. While basic attentional tone is controlled by the interaction among reticular activating system, thalamus, and prefrontal cortex, direction and selection of attention is controlled by neural circuits of prefrontal, posterior parietal, and limbic cortex. It is expected that understanding of attention and its neural could provide answers to the relationship between pathophysiology and clinical symptoms of some major psychiatric disorders. More effort are required to develop tools to assess more detailed and various aspects of attention in Korea.