Liposomes can be made target-specific by immobilizing antibodies on their surface against characteristic components of target organ or tissue. Possible schemes of antibody immobilization on liposomes are briefly considered. The use of immunoliposomes for the targeted delivery of diagnostic and therapeutic agents within the cardiovascular system is discussed. Immunoliposomes are shown to be suitable carriers for targeting blood vessel injuries, lung endothelium, and myocardial infarction. The role of polyethylene glycol in the preparation of long-circulation liposomes is investigated, and a hypothesis explaining the mechanism of polymer protective action in terms of physicochemical properties of diluted polymeric solutions is suggested. Polyethylene glycol-coated liposomes are investigated as possible carriers of imaging agents for gamma and MR visualization of different areas of interest in the body, including lymph nodes. The possibility of simultaneous immobilization of protective polymer and antibody on the liposome surface is proved, and the long-circulating targeted immunoliposomes are used for the targeted delivery of radiolabel to necrotic areas in rabbits with experimental myocardial infarction.