Ferry service is a transport system of regular routes which links areas separated by water bodies. In many occasions this means of transport allows mainland territory of country stay connected to its remote island or peninsula areas. This is especially important to Greece as it has a lot of small islands all over Ionic and Aegean seas. This article aims to describe the spatial structure of the ferry service in the Mediterranean Sea. To this end, for 207 ferry lines passenger and car flows were calculated, as well as the main concentration zones of ferry traffic were identified. The maritime ferry system in the Mediterranean is divided into several separate zones and can be called bipolar. The region stands out as a less busy in Europe but with the biggest number of ferry routes. Greek routes are unique for entire Europe and can be called «bus type routes».