This chapter investigates whether a high level of attention during flow is physiologically distinct from effortful attention. The investigation associates the concepts of flow and flow proneness with the existing theories of emotion, attention, and expertise to arrive at accurate result, and surveys the existing research studies on psychological and physiological correlates of flow and proneness for similar experiences. It examines whether these entities support the view that attention during flow is different from attention involved in mental effort, and discusses how psychophysiology of flow has the ability to explain the relationships prevailing between flow and health. Flow is defined as an experience of “enjoyment and concentration” occurring during challenging tasks that matches in difficulty to the levels of a person’s skill, whereas flow proneness is defined as the habit of a person in experiencing the flow state.