This book presents and discusses the law of third sector organizations in a selected number of European Union countries and in a comparative perspective, with the aim of providing a common basis for further legal analyses or legislative advancements both at the national and supranational level.The book is divided into two parts. Chapters in Part I present the ways in which each national jurisdiction deals with the group of organizations identified by the authors as third sector organizations , regardless of the ways in which these organizations are denominated or are commonly known in each country or the place in which their regulation is found.Chapters in Part II share a synthesis and comparative approach and draw the lines for further developments of the research activity culminated in the book.