This article, which also has a nature of a review, presents issues of knowledge management in virtual organizations. The aim of the study was to identify and characterize the most important issues, i.e. the nature, subject, methods, tools, problems and benefits associated with the process of knowledge management in virtual organizations. The analysis of the literature included both Polish and foreign papers published in the twenty-first century, containing the latest theories and research results as well as classic approaches. The first part of the article describes the concept of virtual organizations, while the second contains the definitions, conditions and problems of knowledge management in this type of enterprises. The study shows the important role of knowledge and information technology, their relationships and the impact on virtualization of organization.