Provided is a method and apparatus for providing a three-dimensional (3D) image. A plurality of first projection images may be created by detecting X-rays which are emitted toward an object at different angles. A plurality of second projection images with respect to a partial volume of the object may be created by applying a forward projection and interpolation to at least one of the plurality of first projection images. A left image and a right image may be selected from among the plurality of second projection images, and the selected left image and right image may be displayed for a user as a 3D projection image.