Abstract: The present invention relates to a contrast medium composition (formulation) comprising a highly concentrated contrast agent for use in an imaging method. The contrast medium composition according to the present invention, which comprises iodine working as a contrast agent in a higher concentration than the concentration used before, shows higher contrast enhancement effect in both of arterial phase and portal phase when used for liver CT than a composition comprising the contrast medium in a concentration used before. Accordingly, images having excellent resolution and discrimination can be obtained.