This thesis analyzes the academic debates about "post-conflict peacebuilding", that is, the kind of peace operations that have taken place since the late eighties in those countries that had suffered an armed conflict. These operations led by United Nations and other international actors, were characterized from the very beginning to mean a quantitative leap and, above all, a qualitative leap leading to these missions to aspire not just to peacekeeping (as during the Cold War) but to the transformation of the different areas of society in which it intervenes (political, social, economic, cultural, etc.).. In academia, these operations have raised an important debate, especially in the last decade. This debate is characterized by a critique of the form and substance of the model of post-conflict peace-building that has taken shape. The main hypothesis of the thesis considers that this critical debate has made four large academic contributions to the debate on peace-building: i) analyzing the metatheoretical model of post-conflict peacebuilding and pointing to the existence of a "liberal consensus" that have come together various ideological currents ii) problematizing some of the main aspects that characterize these operations (the kind of results they achieve, the poor viability of its approach or the real political and domestic agendas of international actors involved), iii) noting the need to put into practice alternative approaches to the dominant model of post-conflict peacebuilding, with particular emphasis on the consideration of the "local" as indispensable aspect in order to build peace, and iv) critically analyzing whether the concept of “local ownership” that emerged in recent years on the international agenda of peacebuilding, can be a formula to improve the sustainability and the legitimacy problems that seem to exist in the model of post-conflict peacebuilding. While the theoretical framework divides into five chapters the features of the post-conflict peacebuilding model and the four contributions to critical debates that have been conducted in recent years, three other chapters analyze in detail whether the case of Sierra Leone is able to show some of the points raised in the theoretical sections. Finally, the thesis provides some conclusions from the case of Sierra Leone and some of the general type used to confirm that, at least the critical contributions have favoured a re-politicization of a debate that was initially addressed in strictly technical terms.