In an experimental trawl fishery, diamond mesh codends made out of 2.5 mm flexible Dyneema twinewere tested. The principle aim was to investigate the effect of the number of meshes in the codendcircumference, the number of twines (single or double), and netting orientation (T0 or T90) on the sizeselection of cod (Gadus morhua), plaice (Pleuronectes platessa) and flounder (Platichthys flesus). In addition,the obtained size selectivity for the codends made of Dyneema netting were compared to results obtainedfor T90 codends made of standard 5 mm single twine PE netting, and to previous results for other PEcodends used in the same fishery. It was observed that the selective performance of the Dyneema nettingcodends was very high compared to other T0 and T90 codends of the same mesh size and number ofmeshes in the codends circumference. This demonstrates the high selective potential of the thin andflexible Dyneema netting compared to nettings which are traditionally used in the construction of trawlcodends. Furthermore, reducing the number of meshes in the codend circumference for the Dyneemacodends significantly increased the size selection of cod but did not affect the size selection of plaiceand flounder. This difference between the species is likely linked to their different morphologies. Nodifferences in the size selection of the T0 and T90 designs made of Dyneema twine tested were observedfor any of the three species. For cod, the effect of using single or double twine in the Dyneema codendswas also tested, however, no significant differences were found.