The relationship between severe early institutional deprivation and scholastic attainment at age 11 in 127 children (68 girls and 59 boys) adopted from institutions in Romania was compared to the attainment of 49 children (17 girls and 32 boys) adopted within the UK from a non-institutional background. Overall, children adopted from Romania had significantly lower attainment scores than those adopted within the UK; the children within the Romanian sample who had spent 6 months or more in an institution had significantly lower attainment scores than those who had spent less than 6 months in an institution, but there was no additional risk of low attainment associated with longer institutional care after 6 months. The lower scholastic attainment in the children adopted from Romanian institutions, as compared with domestic adoptees, was mediated by IQ, and to a lesser degree, inattention/overactivity. When these factors were taken into account, only small between-group differences in attainment remained.