What role does the Peacebuilding Commission of the United Nations, established in 2005, play in post-conflict peacebuilding? Can it meet the high demands placed upon it? The author examines whether the establishment of the Peacebuilding Commission has been able to close the 'peacebuilding gap' within the United Nations system. To this end, she analyzes the history of the Peacebuilding Commission's creation and the founding resolutions for the new commission. She also discusses the first cases addressed by the commission and places the activities of the Peacebuilding Commission in the historical and political context of post-conflict peacebuilding by the United Nations. The chosen approach is interdisciplinary, combining legal studies with political science and historical aspects.