A traditional group of port industry plants which operate in seaports, including the biggest Polish seaports, is made up of the plants importing cheap raw materials by sea. With a direct access to sea transport they use the so-called "scale effect". Since the commencement of the system transformation in Poland these plants have been undergoing organizational, proprietary and functional alterations. One of the most important directions of these changes has been an increase in the importance of services in the functioning of the plants. What is manifest in the case of the fertilizer companies from Police, Gdańsk and Szczecin is that they have been developing their services in order to meet both their individual and external entities' needs, although their industrial operations are still predominant. However, the remaining plants situated in the Polish seaports and analyzed in this article have changed their business activity from industrial operations to services. They have gradually abandoned production and replaced the handling which was carried out solely to meet their individual needs with the development of services provided to external customers and new merchandise. This process has been taking place in relation to the Baltchem, the Siarkopol Gdańsk and the formerly operational Huta Szczecin. It is reasonable to predict that in the future the Polish port industry sector will exhibit growing tendencies towards the increasing importance of: - services complimentary to industrial operations, - services provided to external entities, - situation in which external investors, primarily in the services sector, will oper- ate on the port land which is not used by the ports in order to meet their individual needs, - replacing industrial operations with services.