Different modes of fluorine chemisorption on the surface of single wall carbon nanotubes (SWCNTs) are shown to result in varied tendencies of the F atoms to behave as leaving groups, in the presence of a nucleophilic reagent. Fluorine species in weak interaction with the carbon matrix can be readily displaced and therefore, exhibit enhanced exchange properties, while those more strongly bound to the sidewall resist substitution. Such a tunable reactivity of the F atoms in a fluorotube has been used to selectively replace some of them by hydroxyl functional groups. The scheme illustrated here represents a first step toward a quantitative functionalisation process of the SWCNT surface by hetero-elements.