Herein we present the water assisted chemical vapor deposition (WACVD) growth of highly dense and long forests of carbon nanotubes (CNTs). Annealing of thin catalyst film was done at 600 degrees C and growth of CNTs at a relatively low temperature (700 degrees C). A small amount of pure distilled water (0.04 sccm) was introduced without assistance of carrier gas such as Ar or He during the growth. Initially, water vapor enhances the crystallinity of growing nanotubes and their length increases with growth time. However, the presence of water vapor gradually changes their structure from multiwall to thinner or even single wall carbon nanotubes. After a certain growth time, the growth rate becomes slow and structural disorder start to increase. The electrochemical properties of the obtained ultra-long CNTs forests were analyzed by transferring them on adhesive conductive aluminum tape using a novel methodology. In addition, a water plasma treatment was performed in order to introduce oxygen functional groups on the transferred CNTs (CNTs/Al). The specific capacitance of CNTs/Al increases from 87 to 148 Fg(-1) for untreated and water plasma treated CNTs/Al, respectively. (C) 2014 Elsevier B.V. All rights reserved.