The work reports the detailed investigation of factors affecting crystallization and phase stability of nanosized precursors based on zirconia solid solutions obtained by reversed co-precipitation technique from diluted salts solution and further dehydration (freeze-drying, freeze-drying with glycerol, freezing in liquid nitrogen, drying under overpressure). Basing on simultaneous thermal analysis (STA) data, the criterion for crystallization completeness of the "amorphous phase → crystalline solid solution" transition was suggested. Consideration of STA and X-Ray diffraction technique (XRD) results provides an opportunity to state that freeze-drying favors step character of precursor crystallization, while the use of freezing in liquid nitrogen leads to single step crystallization. Combining XRD results with the data of particle size distribution analysis, it was shown that phase stabilization of cubic zirconia based solid solution at temperatures up to 1000°C is due to the fine powder dispersity in that temperature region.