There are many methods and systems for measuring the particle size distribution (PSD) of metal powders. Metal powder used for 3D printing typically has tight specifications for its PSD as particles above a certain size cannot be spread into the thin layers needed and very small particles degrade flow and can cause dust in the printing system. Unfortunately different measuring systems can give somewhat different results. This investigation aims to show the limitations and differences in results from different measurement systems when measuring PSDs with different breadths and sharpness of cut (e.g. classified c/w sieved powders). The methods tested are laser diffraction sieve analysis and optical assessment.