This paper deals with the importance of the spatial, geographic aspect in analyzing ferry traffic, especially on Croatian islands. The importance of ferry traffic is analyzed within the regional development of the European Union as a whole, as well as through some examples from different states. The analytical part of the paper deals with correlation between the ferry traffic and its two most striking indirect consequences that are present on Croatian islands, and those are demographic development and tourism. There is a close, direct connection between ferry traffic and tourism, as well as between ferry traffic and general demographic trends. Since there is no evidence of correlation between the index of seasonal frequency of the ferry lines (direct reflection of tourism) and the index of change in population trends on Croatian islands analyzed in this paper, the conclusion is that tourism, as the main economic activity on Croatian islands, can ease – but not significantly eliminate – depopulation characteristics of the insular part of Croatia.