The instant thesis is organized in three main parts. The first contains an overview of U.S. law including constitutional issues of the topic focusing on the separation of tax powers between federal and state authorities with special attention to the basis and extent to which a State is entitled to impose levies on business organizations; a brief analysis of federal legislation allowing the pass-through regime; and summary concerning LLC legislation in the States. The second analyzes the application of the main, basic principles of international taxation (such as residence, source rules, application of international treaties, and connected with it the notion of permanent establishment) to the taxation of non-resident members of a U.S. LLC. Considerable attention was also paid to the withholding obligations of the LLC. And finally, the third part discusses the impact of LLCs internal organization to the final tax liability and connected with it possible planning solutions in the international environment. In this thesis. The thesis is limited to the discussion only to LLCs that chose to be treated as partnerships for federal tax purposes because in the case of the other option their tax liability is very similar to an ordinary corporate one. However, in some cases, I have found appropriate to raise some related issues as well.