The purpose of the paper is to illustrate some of the difficulties associated with assessing the environmental performance of logistics systems. The paper focuses on the environmental effects of transports in the logistics system, and elaborates on the complexity of defining an adequate system. Design/methodology/approachThis conceptual paper builds on theory and literature on systems in general, and specifically logistics systems, and the environmental assessment of them. In addition, mini-cases are used to illustrate the analysis. The cases are from different sectors. Primary data was collected through interviews and secondary data through official internet pages and internal documentation.FindingsThe result of the paper is a set of ”learning lessons” which aim at providing a deeper understanding of the system delimitation problem, specifically for the environmental assessment of logistics systems.Research limitations/implications (if applicable)The paper is conceptual, and provides mainly a basis for further research. The illustrations emanate from a limited number of sectors, although the system delimitation problem is of a general nature.What is original/value of paperThe problem of defining system limits is often overlooked, why this paper provides support for a better understanding of the problems of delimitations of a system. The area of environmental assessment of logistics systems is still in its cradle, why this paper also contributes to that research field.