This report provides an overview of the findings from the Nuffield Foundation research project, `Multidimensional child poverty and disadvantage: tackling ?data exclusion? and extending the evidence base on ?missing? and ?invisible? children?. The report sets out the background and rationale for the project; clarifies the aims and scope of the study; describes methods and data; and sets out the key substantive findings for the four groups of children examined within the project. We conclude by drawing lessons and implications from the project and setting out recommendations for tackling the phenomenon of ?data exclusion? and building up quantitative evidence on missing and invisible groups in the future.