This paper compares inter-organizational (IO) interaction and inter-organizational information systems (IOS) in public and private sector. The purpose of the paper is to explore differences and similarities between e-government and e-business focusing IOS and interaction. This is done in order to facilitate learning between the two fields. The point of departure is two case studies performed in private vs. public sectors. A comparative study is made using IO concepts from industrial markets that characterize an IO relationship (continuity, complexity, symmetry, and formality) and concepts that describe dimensions of such relationships (links, bonds, and ties). The results from the comparative study show that there are several similarities concerning interaction in relations between organizations in the two sectors. There are also differences depending on the level of analysis (empirical level vs. analytical level). The study shows the need to be explicit regarding organizational value, end-customer or client/citizen value and the type of objects that are exchanged in the interaction.