Adopted children have been said to be difficult children, scarred by their past experiences in maltreating families or neglecting orphanages, or by genetic or pre- and perinatal problems. Is (domestic or international) adoption an effective intervention in the developmental domains of physical growth, attachment security, cognitive development and school achievement, self-esteem, and behaviour problems? We found through a series of empirical studies and meta-analyses on more than 270 studies that included more than 230,000 adopted and non-adopted children and their parents evidence for the adoption catch-up model . Although catch-up with current peers remains incomplete in some developmental domains (in particular, physical growth and attachment), adopted children largely outperformed their peers left behind. Adoptions before 12 months of age were associated with more complete catch-up than later adoptions in some domains. International adoptions did not lead to lower rates of catch-up than domestic adoptions in most developmental domains. We concluded that adoption is a highly effective intervention leading to massive catch-up. Domestic and international adoptions can be justified on ethical grounds if no other solutions are available. Humans are adapted to adopt, and adoption demonstrates the plasticity of child development. See for example Van IJzendoorn, M.H. & Juffer, F. (2006). The Emanuel Miller Memorial Lecture 2006: Adoption as intervention. Meta-analytic evidence for massive catch-up and plasticity in physical, socio-emotional, and cognitive development. Journal of Child Psychology and Psychiatry, 47, 1228-1245. doi:10.1111/j.1469-7610.2006.01675.x