In order to study systematically the dependence of ZnO crystal size with synthesis conditions, stable suspensions of these nanocrystals were produced in ethanol at temperatures between 0°C and 60°C. XRD characterization of solid products verified the formation of ZnO nanocrystals with no need for any thermal treatment even at a temperature as low as 0°C The significant shift in the position of the XRD peaks in those samples synthesized at different temperatures and aging times, suggested a systematic variation in the dimensions of the ZnO unit cell. FT-IR spectra of washed ZnO crystals showed the bands attributed to acetate species, which are considered to be adsorbed onto the nanocrystals surface. The high monodispersity of the 5-8nm ZnO nanocrystals was revealed by HRTEM analyses of the samples synthesized at room temperature. Lower temperatures of synthesis were conducive to smaller nanocrystal sizes. UV-Vis and PL measurements evidenced the continuous growth of the nanocrystals during aging.