Ms Justice Elizabeth Dunne of the Supreme Court (small picture) is now the chair of the Courts Service Board, which determines policy for the courts body and oversees its implementation.
The post is normally held by the Chief Justice Mr Justice Donal O'Donnell.
The Courts Service said, however, that he had exercised his power under the Courts Service Act 1998 to nominate another member of the Supreme Court to take his place.
“With the establishment of the Judicial Appointments Commission this year, he wishes to dedicate more time to this,” the courts body said.