Liposomes represent globular vesicles composed of an aqueous core and one or several phospholipid bilayers. They can encapsulate hydrophilic or lipophilic drugs used in therapy and diagnostic imaging. Liposomes provide protection of the active substances, sustained or controlled release and also targeted delivery of drugs to specific cells, tissues, organs. Easy oxydation of phosphatidylcholin (lecithin)--the main membrane component--is the limitation of the introduction of liposomes to the medicinal practice in a broader scale. Unsatisfying chemical stability of lecithin has an unfavourable influence on drug and liposome stability. Liposomes decompose during storage and leakage of the encapsulated drug occurs. A review of advantages of application of liposomes in medicine and methods of increasing their stability was presented.