Abstract: IrO2 nanocrystals (NCs) were grown on vertically aligned carbon nanotube (CNT) templates, forming IrO2/CNT nanocomposites, by metal organic chemical vapour deposition using (C6H7)(C8H12)Ir as a source reagent. The surface morphology, structural and spectroscopic properties of the nanocomposites were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman scattering. IrO2 varied from particle- to tube-like NCs as the deposition time increased from 5 to 60 min. The particle-like IrO2 NCs may be used as a protective layer on CNTs, providing stable and uniform field emission application. The tube-like structure may increase the surface-to-volume ratio which makes the IrO2/CNT nanocomposites as an attractive candidate for the supercapacitor application.