The use of copyrighted works is an essential tool for carrying out teaching activities. It is relevant for both teachers, who very often use them to support their instructional tasks, and students, who also make use of them to illustrate their learning activities. The mandatory authorisation of the copyrightholder may represent, in some cases, an exorbitant and unjustified demand (e. g. when the use is really inoffensive or responds to the exercise of fundamental rights and freedoms) or even an unenforceable requirement (either because there is no effective and sufficiently developed market for educational licences -notably on line-, or because is extremely difficult to control the actual utilisation of the work). The recognition of the private and public interests in the use of copyrighted works for educational purposes justifies the certain limitations to the copyrightholders' exclusive rights. This publication analyses the scope of the limitation of "illustration for teachin" incorporated in the Spanish Copyright Law by the Law 23/2006 and other complementary exceptions that may be invoked in educational activities. It reviews the legal framework established in the international treaties and in the Information Society Directive and also considers the laws other EU countries and beyond (notably US and Australia) some of them specifically targeting online education. The PhD thesis supports a flexible interpretation of the requirements foreseen in the Spanish Copyright law and de lege ferenda presents a series of policy options that could help to better conciliate public and private interests.