Like it is increasingly happening with policy-makers in different countries around the world, also the partners of the European Network of National Observatories on Childhood (ChildONEurope) turned their attention to child well-being. On the basis of a decision of the ChildONEurope Assembly the European Seminar on Child Well-Being Indicators, held on 29 January 2009 at the Istituto degli Innocenti in Florence, was organized by ChildONEurope Secretariat in the context of network activities aimed at favouring the exchange of knowledge and information on childhood policies and interventions. Addressing children well-being is overall important today to ensure that their rights and needs are adequately fulfilled, as stated in the United Nations Convention on the Rights of the Child (UNCRC). Furthermore, assessing the quality of children's life is more and more acknowledged to be a crucial factor for the implementation and monitoring of childhood policies able to contribute to the social well-being taken as a whole. The actual trend of the discussion over child well-being indicators seems to strike a balance between standard (traditional) indicators such, as those measuring the levels of education and health and other new indicators more child-centred. These latter are conceived in a child perspective, as for example those taking into consideration the participation of the child itself in effective consultation activities. The aim of this compromise is trying to holistically assess the quality of children's life. The European Seminar on Child Well-Being Indicators succeeded in gathering the most eminent experts on this subject at the international level, giving to all participants a clear overview of the major issues at stake. It also put together some of the most relevant national experiences with regard to the data collection and analysis on children well-being in Europe. As ChildONEurope is a network whose research and analysis activities are policy making-oriented, the approach of the seminar was focused on the impact of child well-being indicators on childhood policies and in particular on how such indicators could support the drafting and implementation of effective interventions in favour of childhood and adolescence. The discussion over the indicators on child well-being started at the beginning of the ‘90s; since then a lot of changes happened in our knowledge over childhood and in our thinking and approach toward children's condition and rights. At present, the importance of the monitoring of the children's well being is not in question anymore, in particular, because, as argued in the conclusions of this publication, the field under observation – childhood condition - represents a reality of steady development and change. Thus, even though the so-called “child indicators movement” developed noticeably in the last two decades, there are still to be faced a number of old and new questions. The ChildONEurope Seminar represents an important moment of assessment of the status of the art: the way done and the foreseeable directions that the movement is undertaking.