The aim of this thesis is to study the expressions of Swedish Library managers about the use of volunteers in public libraries: 1, their views on advantages and disadvantages with volunteers, 2, what tasks they think can be placed on volunteers. 3, how the volunteers work is organized, 4, how library operations are affected by the use of volunteers. The purpose is to understand the impact volunteers has on public libraries and through Michnik´s modification of Coblentz’ tree aspects of sustainable organizations discuss how this can affect the public library as an organization. Semi-structured interviews were conducted with three Library Managers and recorded in Zoom. The data were analyzed with qualitative data analysis and then discussed based on the concept of sustainable organization. The study shows that the Library Managers have both positive and negative attitudes towards volunteers. According to the Library Managers volunteers can both strengthen the relationship between the public library and the local community and the citizens' engagement in their library. The Library Managers finds that volunteers contribute with competence and new perspectives to the public library. But according to the Library Managers the public and some politicians have a very shallow understanding of what the public library is and what librarians do. This makes the Library Managers fear that librarians in the future might be replaced by volunteers to cut costs. The thesis shows that volunteers can contribute to – but also undermine – the sustainability of the public library as an organization.