The character is described of various prerequisites for and obstacles against fulfilment of the polluter pays principle in the case of decommissioning of old nuclear research and development (R&D) facilities, and the relevance to other areas is analyzed. Background is compiled in the areas of Swedish old nuclear R&D facilities, environmental liabilities in some areas, and legislation. Two completed decommissioning projects and two under planning are described together with some findings on planning for decommissioning and on cost estimation. Also, an example is given on developing a basis for regulation relating to small facilities. It is concluded that although the polluter pays principle is easy to understand, it may be complicated to implement, especially in cases where there is a gap in time between the operations and the decommissioning. Pitfalls may be plentiful and extensive awareness and substantial efforts are warranted for adequate funds to be available at the time when they are needed. Thus, it is essential that internationally available advice and knowledge be utilized, information exchanged, and necessary knowledge acquired. It is also important to realize that the planning is usually dictated by the needs for financial planning, and that there is a substantial difference between end of license and end of liability. A need for information exchange between different areas of technology is identified and it is hoped that the present work might contribute to such processes.