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Grain-size analysis has long been used as a descriptor of transport and depositional processes. This paper presents the possibility of using image-based granulometries, not yet widely used in the earth sciences, to characterize granulometric composition of unconsolidated estuarine and marine sediments. To test the method, conventional sediment analysis of siliceous and calcareous sediments are compared to image-based analysis of sediments obtained along the O¨re estuary (Northern Sweden) and the Adriatic Sea (Croatia and Italy). These grains have different textural characteristics, composition, roundness and specific surface area. Granulometric parameters are calculated using both a graphical method and the mathematical method of moments. Grains have been imaged using a microscope and mathematical granulometries have been applied to the digital data. Image-based granulometric moment descriptors are compared with sieve + Coulter counter-derived moments. Although it is not claimed that digital-imaging should be the only method used in sedimentology, the results show the potential of applying digital electronic imaging to granulometric analysis of sediments. In this way, sampling for granulometric analysis and sieving processes combined with Coulter counter analysis of fraction <32 μm could be eliminated and a large area of sediment surface could be covered in a short time. [Copyright &y& Elsevier]