Paedophile priest Fr Brendan Smyth will be the subject of a focused investigation as part of a public inquiry into historical child abuse in Northern Ireland.
The serial child molester frequented Catholic residential homes and was convicted of more than 100 charges of child abuse.
Retired judge Sir Anthony Hart is leading one of the UK's largest inquiries into physical, sexual and emotional harm to children at homes run by the church, state and voluntary organisations.
He said the inquiry will "examine issues arising from the actions of Fr Brendan Smyth in a number of homes in Northern Ireland - actions which have been described by a number of witnesses who have already given evidence to the inquiry".
The Historical Institutional Abuse (HIA) inquiry has extended its work to cover three more state-run institutions: Hydebank Young Offenders' Centre in south Belfast and former homes at Fort James and Harberton House, Derry.
Smyth, who was at the centre of one of the first clerical child sex abuse scandals to rock the Catholic Church in Ireland, was convicted of more than 100 child abuse charges relating to a period over 40 years on both sides of the Border.
Despite allegations having been investigated as far back as 1975 by church officials including former Irish primate Sean Brady, it was almost 20 years before he was jailed.
Instead, the cleric, a member of the Norbertine order, was moved between parishes, dioceses and countries, where he preyed on victims as young as eight.
He died in prison in 1997 following a heart attack.
The HIA module focusing on his actions will commence on June 22nd and is expected to conclude by the end of the month.
A representative of the Sisters of Nazareth nuns has accepted the Belfast priest visited Nazareth House and Nazareth Lodge residential homes and sexually abused children.
The inquiry has also heard he was among the offenders at Rubane House boy's home in Kircubbin, Co Down.
Sir Anthony said: "Today we wish to announce that we are adding three more institutions to the list, and one individual, bringing the total of homes and matters to be investigated to 18."
Fort James and Harberton House, both statutory homes in Derry, would be dealt with together in module five, to take place next month, he said.
The treatment of children in church-run residential homes is a key concern of the investigation, which is considering cases between 1922 - when Northern Ireland was founded - and 1995.
Victims have alleged they were subjected to physical, sexual and emotional abuse.
The inquiry does not have the power to find anyone guilty of a criminal offence, but if the tribunal does unearth evidence of any crimes committed, the material can be passed on to the PSNI).
In total, the inquiry is expected to hear from more than 300 witnesses during the public evidence sessions.
It is required to complete its hearings and all investigative work by mid-summer 2016, and has to submit its report to the Northern Ireland Executive by January 17 2017.
Among its recommendations could be compensating victims who have alleged they were abused.
Press Association