There is a need to define the role of the library in the development and implementation of open science, based not only on the widespread concept of open access to scientific publications, but also on other principles. UNESCO’s concept of open science is presented in relationship with the concept of open knowledge analyzed in the context of three approaches: 1) “openness” from the point of view of copyright (unrestricted reading, distribution, processing of the original work and publication of derivative works); 2) scientific communication (interpretation of knowledge and its transfer between different scientific disciplines, governmental structures, social actors, non-scientists and non-scientific institutions, as well as publicly accessible communication); 3) open, comprehensible, verifiable knowledge, accessible to all members of society by means of well-known criteria. The directions of libraries' activities within the framework of open science are proposed. Some of the competences necessary for such activities are fixed in the professional standard “Specialist in Library and Information Activities”: the ability to organise a multifunctional library space, analytical and synthetic processing of documents, etc. The competences of the library specialist are also required. In addition, the library specialist needs additional knowledge about the essence of open knowledge (open scientific knowledge) and its key components, the basics of intellectual property legislation, the basics of research ethics, the organisation of open reviewing, the use of altmetrics, the organisation of open learning platforms. Taking into account the amount of knowledge and skills required, as well as the specificity of their application areas, it seems reasonable to train first of all employees of scientific, scientific-technical, and university libraries.With the new competences, library professionals will be able to contribute to the effective integration of their institutions into the research process. The library can become a real driving force for open science.