This study investigated the potential association between symptoms of reactive attachment disorder and language difficulties among internationally adopted children in Finland (the FinAdo study). The language difficulties were assessed using a standardised Five to Fifteen (FTF) parental questionnaire and the symptoms of reactive attachment disorder using a FinAdo questionnaire. The study sample consisted of 689 6-15 year old children (49.2% boys, response rate 48%). Twenty-nine percent of the children were reported to have language difficulties and 8% severe language difficulties (10% and 2%, respectively, in the general population). A child's symptoms of reactive attachment disorder were associated with language difficulties and severe language difficulties, OR 2.15, 95% CI [1.39, 3.31] and OR 4.33, 95% CI [1.57, 11.98], respectively, the associations being robust to adjustments for background factors. (Contains 6 tables.)