Ytteria-stabilized zirconia powders from different sources were used to investigate powder packing characteristics and subsequent sintering behaviour. Powders of different levels of agglomeration were controlled by varying degrees of ball-milling, followed by shaping through colloidal casting. Experimental findings revealed that the average pore diameter of the powder compacts appears to be a good representative of the whole pore structure of the green compacts. This pore parameter exhibited a well-defined correlation with respect to the initial mean powder size for each type of powder, irrespective of the difference in particle size distribution and degree of agglomeration, and also correlated soundly with the sintering behaviour of the powder compacts. Critical pore diameter/particle size ratios were experimentally determined, which were shown to be strongly related to the initial particle size by a power-law dependence. This dependence offers an excellent prediction of the critical ratio in alumina powder compacts reported by Zheng and Reed [27], which further supports the feasibility of this relationship.