There are 21 children in specialised care placements abroad because their needs cannot be met in Ireland.
This is costing about €2.2 million a year.
According to Tusla, there are a small number of children who need specialised care because of their life experiences.
On rare occasions, a child or young person may be placed in out-of-state care at a facility abroad that offers a broader range of treatment options.
According to the latest figures from the Child and Family Agency, this is the case for 21 kids at present.
20 children are being looked after in the UK and one child is in Spain.
The chief executive of Barnardos, Suzanne Connolly, says the situation is far from ideal.
"The children we are particularly concerned about are the children who are placed in residential care abroad," said Ms Connolly.
"Some of those children will have very violent behaviour which has put them at risk personally and put others at risk and also mentally as they can come into contact with the criminal justice system.
"So they are placed in specialist residential facilities in the UK."
Tusla says the approximate cost of caring for these 21 children abroad is about €183,500 a month.
Ms Connolly said there can be serious problems if children are in long-term care abroad.
"When they have stayed there - sometimes for several years - and received their treatment they then come back to Ireland and they have lost all contact with their own network.
"Then they are extremely vulnerable to homelessness and to poor mental health themselves.
"So we would be very concerned about that cohort of children and we need to have the facilities to meet their needs here in Ireland."