1. An X-ray imaging apparatus comprising: an X-ray generator to generate X-rays and irradiate an object with the X-rays; an X-ray detector to detect X-rays irradiated from the X-ray generator and transmitted through the object; and a host device to generate and display at least one of X-ray images from the detected X-rays, to extract at least one of bone image information and soft tissue image information corresponding only to a region selected by a user from the X-ray images when selection of the region of the displayed X-ray image is input from the user and to display an image containing the at least one of bone image information and soft tissue image information of the displayed X-ray image.