New demands of the environment represent a constant effort for public libraries in the process of monitoring and adjusting of their activities. A relevant responsiveness is one of the important elements in this process. However, introducing a new activity or introducing changes also mean a burden. Some long-term procedures and strains in this process can be avoided or abridged by following the rules and elements of the systems theory. The systems theory allows the comprehension of interaction and connection of elements forming every natural of artificial system which also represent public libraries. Due to the unified principles of functioning of these systems it is possible to predict and plan the reaction of the system. So, the unified scheme of elements of the systems theory enables a simplification of planning and implementing of changes. Therefore the introduction of any new activity or adjustment does not require a set up of an entirely new system; the new demands are included into the existing system represented by the concrete public library. Applying the principles of cybernetics and the feedback loop allow a simultaneous monitoring of these changes. Under the observance of the valid standards for the Slovenian public libraries single elements of systems theory have been applied and introduced in the environment of the Ivan Tavcar Library in Skofja Loka.