Dry treatment using a combination of UV and ozone can readily change the surface of vertically aligned carbon nanotubes from superhydrophobic to superhydrophilic. This treatment is also effective for buckypapers. Heating in a vacuum at an elevated temperature (650-750 °C) can reverse the surface state from superhydrophilic to superhydrophobic. The UV & ozone treatment causes the least amount of damage to the stripe-like carbon nanotube patterns. The effect of rough surface on apparent contact angles of CNT forests was discussed to explain the origin of superhydrophilicity and superhydrophobicity.