Objective: To evaluate the translucency characteristics of new flowable bulk-filling resin composites at various thicknesses. Experimental short fibre-reinforced composite was also tested. Methods: Two new brands of flowable bulk composites (Venus Bulk Fill and SureFil SDR Flow), experimental short fibre-reinforced resin composite (FC) and, as control, conventional flow (Filtek Supreme Flow XT A3) and universal (Filtek Universal Supreme XTE A3B) resin composites were investigated. Translucency parameter was calculated for various thicknesses of composite (1, 2, 3, 4, 5 and 6 mm) over white and black backgrounds using spectrophotometry to determine the CIELAB values of each specimen. Data were statistically analysed with analysis of variance. Results: Translucency values significantly correlated with thickness of resin composite specimens (P 0.05). For the new types of flowable bulk-filling material, translucency was observed for thicknesses up to 5 to 6 mm, whereas for experimental FC composite, the effect was observed up to 4 to 5 mm, and for control flow and universal filling composites, up to 2 to 3 mm. Conclusion: New flowable bulk-filling resin composites have less masking ability than conventional universal filling resin composite materials, which should be taken into account when optimum colour match and aesthetic results are to be achieved. Palabras clave: translucency, flowable resin composite, universal resin composite