We report on a comparative study of electron transport properties in single-walled carbon nanotubes (SWNTs) and SWNTs filled with Buckminster fullerenes, C60@SWNTs. The single wall carbon nanotubes exhibit field effect induced by a n+Si gate separated from the SWNT by a 300 nm SiO layer. At low temperatures the metallic SWNTs exhibit Coulomb blockade effects and Luttinger liquid behaviour. In order to asses the effect of C60 inserted in SWNTs we have prepared defect-free SWNTs with a narrow diameter distribution 13.9-15.1Å, which allowed the assembly of C60@SWNTs in high yield (~90%). Systematic transport measurements from room temperature to liquid He temperatures in individual C60-filled SWNTs revealed unchanged Luttinger behaviour but a reduced transmission compared to the empty controls.