The UK will take in up to 3,000 refugees, mostly vulnerable children, from the war-torn Syria region by 2020.
The government called the move the "largest resettlement programme for children in the world".
It is in addition to UK prime minister David Cameron's pledge to take 20,000 refugees by 2020.
But critics said it would do nothing to help the thousands of lone refugee children who had made it to Europe, but were at risk of trafficking and abuse.
The government scheme will target unaccompanied children in the Middle East and North Africa, as well as those considered at risk of abuse and exploitation, such as children threatened with child labour and child marriage. It will resettle children and their families "where the UNHCR deems resettlement is in the best interests of the child." 'Exceptional circumstances'
Several hundred people are expected to be resettled in the UK by April 2017 "with a view to resettling up to 3,000 over the lifetime of this Parliament", the government said.
The five-year Syrian civil war has created more than 4.5 million refugees across the region - half of them children in need of food, education and a home. The UN has warned that a whole generation of Syrian children is at risk.
Immigration Minister James Brokenshire said: "We have always been clear that the vast majority of vulnerable children are better off remaining in host countries in the region so they can be reunited with surviving family members. However, there are exceptional circumstances in which it is in a child's best interests to be resettled in the UK.