The Port of Rijeka is an important transport hub of international importance for the Republic of Croatia. With its geostrategic predispositions and increasingly strong appearance in transport sector, the Rijeka gateway is gaining more and more significance. As a key hub between the maritime and inland traffic systems, the Port of Rijeka encompasses a whole range of active and passive participants in process of creating port services. Positive economic effects of the port’s traffic on its regional area are manifested through multiplicative effects arising from participation in port services. By calculating different multiplicative effects, it is possible to get a better insight into commercial-economic interconnection of port services providers within the Rijeka port system. This paper confirms that the revenues generated by the traffic of cargo and passengers achieve 3 to 10 times greater effect on the overall market, and directly or indirectly influence at least 0.15 % to at most 1.55 % of the national GDP.