The distribution of port traffic in Spain has traditionally shown high levels of concentration, especially for containerized cargo. However, the container movements as a whole hide a differential nature of containers’ flows: container movements: between Spanish ports (national cargo), between international ports (export and import cargo), or simply movements of containers using the port as a logistics platform (cargo in transit). In this paper, we have analyzed the evolution of concentration in the global container traffic (TEUs). The reference period is 2007 (such as immediately preceding the commencement of the economic crisis in 2008) and 2015. We calculated Herfindahl indices and Gini and on the three kind of movements (the national, the import-export and the transit cargo), in order to make a distinction between the concentration sources, related to the type of movements. So, the possible port specialization is analyzed. The results confirm the differential behavior of different types of traffic, as well as the specialization and headship of the ports authorities.