Most research groups working with LNPs use Zetasizer instruments, since they are capable to determine both particle size and -potential. However, the Malvern Zetasizer instruments have limited compatibility-which is crucial for online measurements-with Wyatt light scattering devices and vis versa. The Instrument setup and other parameters (e.g., laser wavelength, measuring angle(s), calculation algorithms, etc.) can differ between manufacturers or instrument models, which can have a significant impact on the measurement outcome. Our Zetasizer Nano-ZS and Dynapro™ NanoStar detectors differed in laser wavelength (632.8 vs. 658 nm), laser power (4 vs. 120 mW), detector angle (175° vs. 90°), and the manufacturer-specific algorithms to treat the data. We therefore assessed comparability between the two devices using PS particle standards with radii of 15 and 50 nm, respectively. Both devices were able to accurately determine particle size of the standards within an error of 5% (Table ). For LNPs, the obtained Z-average sizes varied by 5-10% between the two devices. The four investigated LNPs are in the typical size range for LNPs, i.e., Rh = 79, 116, 94 and 146 nm (Zetasizer ZS nano) and Rh = 72, 120, 105 and 155 nm (Dynapro™ NanoStar) for LNP-1, LNP-2, LNP-3 and LNP-4, respectively. We noticed that the Dynapro™ NanoStar tended to provide broader particle size distributions and a small shift towards higher Z-average sizes compared to the Zetasizer ZS nano (Table and Figure ).