Abstract: Purpose – The purpose of this paper is to present an approach to support understanding of inter-organisational systems. Design/methodology/approach – The approach combines two types of graphical snapshots of relevant properties of each organisation, based on concrete data. The first type of snapshot provides a bird's eye view of the network that enables matching partners to form groups based on similarity. The second type of snapshot can be used to compare and contrast the information technology (IT) portfolio of partners to assess the extent to which each portfolio is ready to meet the needs of the inter-organisational system. The approach has been applied in a case study that analysed E-CUSTOMS, a large distributed system that connects the customs organisations of a number of member states of the European Union. The approach has been validated by showing the results to experts in the E-CUSTOMS project, who confirmed the findings. Findings – An approach based on quantifiable and non-quantifiable data that combines two visualisation techniques was used. The graphical snapshots obtained by applying this approach showed similarities and differences between countries that indicate opportunities and challenges in IT integration. Practical implications – The approach provides a semi-automatic method to understand inter-organisational systems. If in need of successful co-operation in groups within an inter-organisational network, this approach will help the expert to ask the right questions. Originality/value – An understanding of inter-organisational systems is necessary, as co-operation in inter-organisational networks usually requires considerable up-front investments in IT specific for this co-operation.