The purpose of this book is to analyze the tax treatment of Collective Investment Schemes (CISs) and trusts from a Swiss and international tax law perspectives from a theoretical and practical approach, focusing on case studies. CISs and trusts (« hybrid entities » as per OECD’s wording), together with other cross-border business structures, have become the center of attention of both scholars and practitioners. Despite that, there are still a number of uncertainties regarding the tax treatment of such hybrid entities at a Swiss domestic and international tax level, particularly as to the applicability of Double Taxation Conventions (DTCs) to such hybrid entities. This book addresses the main tax aspects of CISs and trusts but also highlights the issues that arise when attempting to effectively implement them and offers proposals and solutions to address such difficulties. The book begins with a general introduction outlining the key aspects of the study, and then continues with an in-depth analysis of the direct taxation of CISs and foreign trusts in Switzerland. Thereafter, the book offers a critical analysis of the potential double taxation resulting from the existing ambiguity in terms of DTC access to CISs and trusts. The study then shifts to a meticulous analysis of the key elements that need to be present for any wealth management structure to benefit from DTCs: « person », « resident », « attribution of income », as well as the complex definition of « beneficial owner ». These criteria are then applied for purposes of determining whether CISs and trusts in particular can benefit from DTCs. Finally, the study offers a conclusion and proposes solutions that CISs and trusts should be granted access to DTC provisions, particularly in regards to the OECD Model, its Commentary and other OECD materials.