Abstract: Macrophages within the tumor microenvironment, also called tumor associated macrophages (TAMs) have been shown to play a major role in the growth and spread of many types of cancer. Cancer cells produce cytokines that cause the macrophages to differentiate into an M2 subtype. We have designed a mannosylated liposome (MAN-LIPs) and successfully showed it to accumulate in TAMs in a mouse model of pulmonary adenocarcinoma. These liposomes are loaded with 64Cu to allow tracking by PET imaging, and contain a fluorescent dye in the lipid bilayer permitting subsequent fluorescence microscopy. MAN-LIPs are a promising new vehicle for the delivery of imaging agents to lung TAMs. In addition to imaging, they hold the potential for delivery of therapeutic agents to the tumor microenvironment.