This chapter aims at highlighting the relationships between air, maritime & logistic activities of port cities in Europe. Although recent studies have considered sea-air intermodality as a locational advantage for ports and coastal urban centres, they are still few and isolated case studies. Nevertheless, this subject appears to be of growing interest for transport, logistic players and urban planners to improve port performance in a competitive context. However, there is neither an estimation nor a comparative analysis on effective air-sea relations within port city nodes. We propose a valuation of such potentials based on available and comparable data at a European scale, such as air and maritime traffics, urban population, and employment in specific transport activities (freight forwarding, logistics, warehousing, port and airport services). This innovative approach focuses on the level of interdependency between airports, ports and cities. It shows that air-sea linkages within European port cities are still not strongly interdependent