Ports play a crucially important role in the development of national economy as they generate stable tax flows and duties, providing direct positive effects on GDP, Balance of Payments and Balance of Trade. Sometimes their impact on regional economy may be significant also. The analysis of the structure of cargo volumes (annual throughput) transshipped by the port and changes in commodity mix can provide an invaluable insight in the trend of port development. The comparative analysis of the structure of cargo volumes at Latvia’s ports has been done in the paper and the degree of its dissimilarity was statistically evaluated.