The article analyzes the spatial and economic forms of marine port agglomerations. The notion ‘port agglomeration’ and genesis of different sea port agglomerations have been reviewed. Theoretical basis of the analysis is presented by the works of V. N. Obraztsov, S. V. Zemblinov, I. Tyunen, S. Zamansky, M. Porter et al. Transport processes, arrangement of transport junctions, assessment of their influence on the performance of the regional economics have been stated to take importance in the research conducted by the scientists. The detailed economic characteristics of a transport hub, regional sea transport and logistic complexes, transport and logistics cluster and special economic zones of the port type has been given. The concept of cross-border sea transport and logistic clusters has been formulated; their typology according to economic grounds has been developed. As a result of the statistical analysis of cargo turnover in the Russian ports there came out two clusters with great cargo turnover. There have been given data about the large Russian ports: Novorossiysk, Ust’-Luga, Port Vostochny, Primorsk, Port St. Petersburg, Murmansk, Port-Caucasus, Vanino, Tuapse, Nakhodka. It has been inferred that the great number of ports function as port junctions and need investments and modernization of the main production assets. The Russian sea transport and logistic complex is a part of the global transport system, in which can be seen similar changes and lagging from the developed countries. Very few of the Russian ports develop dynamically and can be reorganized into the transport- logistic clusters.