Speaking during an annual mass for the Disappeared in St Patrick's College, Armagh, Archbishop Eamon Martin said he hoped the bodies of four people who were kidnapped, killed and secretly buried by republicans during the 1970s and 1980s can be found.
He said: "I appeal to the conscience of anyone who has information that might help find the others to come forward to the Independent Commission for the Location of Victims' Remains (ICVLR), so that, even at this late stage, the remaining families can experience the consolation of being able to offer a Christian burial to their loved ones."
An independent body created during the peace process, the ICVLR has so far recovered the remains of 12 people.
The remains of Cistercian monk Joe Lynskey, who was snatched from West Belfast in 1972, are yet to be found.
Columba McVeigh (abducted in Dublin in 1975), SAS-trained Captain Robert Nairac (vanished from a South Armagh pub in 1977) and Seamus Ruddy (went missing from Paris in 1985) also remain missing.
Archbishop Eamon Martin added: "Over the past 17 years, the families of those abducted, murdered and secretly buried have gathered to comfort one another and a close bond of empathy has developed among them.
"It is particularly merciful that many of those who have already had the comfort of bringing home for burial the bodies of their loved ones, continue to gathered in support of the remaining families who still wait in hope.