Internally displaced children are twice invisible in global and national data. First, because internally displaced people (IDPs) of all ages are often unaccounted for. Second, because age-disaggregation of any kind of data is limited, and even more so for IDPs. Planning adequate responses to meet the needs of internally displaced children, however, requires having at least a sense of how many there are and where they are. This report presents the first estimates of the number of children living in internal displacement triggered by conflict and violence at the global, regional and national levels.