The article is devoted to determining the area of public domain and problematic issues of its application. In theory, legal regime of public domain provides modern society with a wide range of opportunities of intellectual property use, however, regulation of this regime and even its definition may differ from country to country, which creates legal uncertainty. The well-known principle idea/expression dichotomy which declares that all ideas should be free to use, may show the sphere of public domain in general,but it does not permit to determine the area of this regime precisely. In the narrow sense, public domainis a specific regime for situations where existing exclusive right to work expired or ceased to exist on any reason. In this case, we have a specific legal regulation rather than absence of legal regulation at all. This may provide a public control for use of intellectual property and, at the same time, avoid monopolization. However, practical application of the public domain regime is limited by a number offactors, in particular, limited access to the object, existence of protecting elements inside the work,specific technical conditions of its use, territorial limitation of exclusive right, etc. In order to provide effective use of the global humankind heritage, these factors should be reflected in legal documents at the international level. Unfortunately, currently there is clear shortage of international regulation ofthe public domain regime. National legislation (including the Russian one) as a rule does not provide necessary legal support either. As a result, society may not obtain proper access to results of creative activity of its members.