Super-hydrophobic carbon nanotube (CNT) powders were formed by NF3 glow-discharge plasma at low-pressure and their surface free energies were directly determined from the contact angles with probe liquids using the Owens-Wendt plotting. The cushion made of plasma-treated CNT powders revealed super-hydrophobicity (contact angle > 153 degrees), regardless of kinds of probe liquids and treatment-time. The surface free energy of the NF3 plasma-treated CNT powders decreased drastically from 82.6 to 0.12 mJ/m(2). The plasma treatment using fluorinated compound gases may be useful for dispersing, separating, and cutting CNTs since CNTs have tendency to aggregate in bundles and poor solubility. (c) 2006 Elsevier B.V. All rights reserved.