Liposomes are nanocarriers consisting of a phospholipid bilayer, similar in composition and structure to a cell membrane. Such a feature provides several possibilities related to the transport and delivery of biologically active substances to the specific cells in organisms. It is now becoming more and more popular to modify lipid carrier shells to achieve higher specificity and efficiency of transport into cells, and to reduce immunogenicity. The article aimed to present the properties, characteristics and application of liposomes modified with polyethylene glycol (PEG). The most common modification is a coating of liposomes with PEG, then sterically stabilized PEGylated vesicles are formed. PEGylation is currently a pillar of liposomal technologies due to the high efficiency of this type of nanocarrier and the possibility of attaching ligands to polymer chains. This article presents the characteristics of liposomes as carriers of substances, their structures, and types of cell interactions with a special emphasis on PEGylated liposomes.