Nanostructured ZnO (without stabilizers) has been synthesized using conventional (non-ultrasound i.e. NUS) as well as sonochemically assisted (US) synthesis method. Zinc nitrate hexahydrate (Zn(NO3)(2)center dot 6H(2)O) and sodium hydroxide (NaOH) have been used as raw materials (synthesis precursors). Zinc nitrate hexahydrate reacts with sodium hydroxide at room temperature (35 +/- 2 degrees C) to form ZnO powder. It is found that equilibrium conversion occurred in a shorter time in sonochemically (US) assisted method when compared to conventional (NUS) method. The ZnO powders synthesized by both the methods have shown to have nanometric-sized crystallites. It was found that the crystallite size of the sonochemically (US) synthesized ZnO and conventionally (NUS) synthesized ZnO are 23 +/- 1 nm and 32 +/- 1 nm respectively. The FTIR spectra analysis confirms the occurrence of the reaction to form Zinc Oxide by both NUS and US methods. Needle shaped structures agglomerated in the forms of bundles were also found in SEM micrographs. It was found that sonochemical synthesis method have saved more than 90% of energy utilized by conventional synthesis method along with the reduced in the reaction duration by 110 minutes.