In a longitudinal study, internationally adopted children (N = 146) placed before 6 months of age were followed from infancy to age 7. Results showed that girls were better adjusted than boys, except in cognitive development, and that easy temperament was associated with higher levels of social, cognitive, and personality development and fewer behavior problems. Higher quality of child-mother relationships, in terms of attachment security and maternal sensitivity, uniquely predicted better social and cognitive development. The combination of attachment disorganization and difficult temperament predicted less optimal ego-control and lower levels of cognitive development. It is concluded that even in adopted children, who are not biologically related to their adoptive parents, early mother-infant interactions and attachment relationships predict later socioemotional and cognitive development, beyond infant temperament and gender.