Covalent functionalization through pure molecular gaseous fluorinationhas been applied on carbon nanofibres. Nuclear magnetic resona nce and thermal gravimetric analysis investigations have been per- formed on fluorinated carbon nanofibres in order to determine the chemical and thermal stability of the C-F bonding. The high covalency obtained allows no significantmodificationof the physicochemical nanostructure of fluorinatedcarbon nanofibresafter sonification.Such modificationof surface chemistry leads to a high increase in the limit concentr ation of dispersed carbon nanofibresin organic solvents without surfactant. An exciting maximum of 570 mg L 1 of fluorinated nanofibrescan be homogeneously dispersed in N-methylpyrrolidone, whereas 310 mg L 1 is the maximum for non-fluorinated carbon nanofibres. In order to understand such dispersibility differences, Hildebrand and Hansen solubility the- ory has been used.