The primary objective in this paper is to present a framework to understand the structure of consciousness. We argue that consciousness has been difficult to define because there are different kinds of consciousness, hierarchically organized, which need to be differentiated. Our framework is based on evidence from adult focal lesion research. The different types of consciousness are associated with distinct brain regions, with the higher levels of consciousness related to self-awareness and theory of mind (both facets of consciousness), with an emphasis on the role of the frontal lobes. The secondary objective is to use this structure to suggest hypotheses about the potential effect of frontal dysfunction at various developmental stages, and including both congenital and acquired brain injury.