Five different measuring methods were used for particle size analysis of nano-dispersed ZrO2 powder and the results were compared. Therefore, aqueous ZrO2 suspensions were analyzed by laser diffractometry, dynamic light scattering (DLS heterodyne and PCS), sedimentation in a centrifugal field, and by ultrasound spectroscopy using different solid concentrations to determine the particle size distribution. SEM analysis was used for determining the primary particle size of the powder (approx. 40 nm). Only secondary particles in the range of 105nm to 224nm were detected by use of the chosen measuring methods, indicating the presence of aggregates or hard agglomerates.