In the present work we investigate the wetting behaviour of nanotubular TiO2 layers (pi-TiO2) grown by electrochemical anodization of Ti. As-prepared pi-TiO2 layers show a super-hydrophilic behaviour while pi-TiO2 layers covered by octade-cylphosphonic acid (C18H37PO(OH)(2)) monolayer show super-hydrophobic behaviour. We demonstrated that the wetting properties significantly depend on the nanotube diameter.