Born on 7 December 1931 in Seoul. He studied in Seoul and Hong Kong.
He was ordained to the priesthood on 18 March 1961 and held various teaching, pastoral and administrative positions in the archdiocese, before going to Rome in 1968 to study canon law.
He was appointed Bishop of Ch'ongju on 25 June 1970 and consecrated on 3 October 1970. He was elected President of the Korean Episcopal Conference. Pope John Paul II transferred him to be Archbishop of Seoul on 29 May 1998. Pope Benedict XVI created him Cardinal in the consistory of 24 March 2006.