In this study, the effects of the different structures and properties of yarns produced with vortex and open-end (rotor) spinning systems on the colour efficiency of package dyeing were investigated. For this purpose, 100% combed open-end and vortex yarns with different linear densities were produced from the same raw material blend and wound on perforated plastic dye tubes (cones) according to the principle of loose winding (package density: 370 g/dm(3)), and the physical properties of the yarns were tested. The bobbins were dyed with reactive dye at three different dyebath concentrations in a universal package dyeing machine and then dried with a high frequency drier. The colour strengths (K/S) and differences (Delta E) were measured by a spectrophotometer. The test results were analysed using statistical methods. In conclusion, the unevenness, total imperfections and hairiness values of the vortex yarns gave better results compared to the rotor spun yarns. It was determined that vortex spun yarns have darker shades than rotor spun yarns, and the effect of yarn physical properties on finishing was found to be significant.