It is intended to provide a liposome preparation which is a liposome, has a lipid bilayer membrane composed of an inner membrane constituted by a lipid including one or more types of functional lipids (a lipid capable of chemically interacting with another compound such as a charged lipid, a polarizable lipid, a lipid-soluble lipid or a water-soluble lipid) and an outer membrane constituted by a lipid with or without including one or more types of functional lipids, and is characterized in that at least a condition that the amount of any one type of functional lipid contained in the inner membrane is larger than in the outer membrane is satisfied. The liposome preparation is suitable as a liposome for encapsulating a contrast agent (a neutral substance having a hydroxy group), siRNA (an anionic substance) having an anticancer activity or the like. Its encapsulation ratio of drug agents, dispersion stability, control release and the like have been improved.
