Though there might be no particular Buddhist concept which highly similar to the Christian understanding of God, it does not mean that Buddhism is irrelevant to the Christian theological reflections on the doctrine of God. Through taking Paul Tillich's concept of ultimate concern as a mediating concept for the comparative studies and/or dialogue between Christianity and Buddhism, one may find that Buddhism has is own views of the ultimate, including the understandings of ultimate reality or ultimate truth in early Buddhism, the Middle-Path School, the Hua-yen School, and the Pure Land School of Mahayana Buddhism. These understandings of the ultimate can provide new perspectives for the theological reflections on the Christian doctrine of God, including the issues of: (1) the relationship between Greek philosophy and Christian theology, (2) the divine relationality, (3) the divine Personhood, and (4) the divine unity and plurality.