Well-aligned ZnO nanorods were synthesized using metalorganic chemical vapor deposition. Their size was controlled by adjusting the O/Zn precursor ratio. The electrical transport and optical properties of the size-controlled nanorods were investigated. The elelctron concentration and electron mobility in the nanorods are not sensitive to the change of the precursor ratio. In addition, the photoluminescent property is nearly the same regardless of their different sizes. These results suggest that altering the precursor ratio is a way of fabricating size-controlled ZnO nanorods with quite consistent electrical and optical properties.