We here present the details of fullerene filling inside double-walled (DWNTs) and multi-walled carbon nanotubes (MWNTs) and also demonstrate plasma ion-irradiation effects on various kinds of nanotube structures. It is found that both the degree of the structural deformation and the fullerene filling efficiency are directly proportional to the applied bias voltage and plasma density used. In particular, in the case of relatively low substrate-bias application, irradiated fullerenes are only adsorbed on the surroundings of the DW/MWNTs, which are kept under end-cap structure. However, it should be noted that fullerene-like material filled DWNTs are shown to be formed by relatively high substrate-bias application, which frequently provokes nanotubes to form open-end structures. (C) 2004 Elsevier B.V. All rights reserved.