An electrochemical and EPR study is reported on two isomeric C-60 derivatives containing a covalently linked free radical TEMPO: a fulleroid and a methanofullerene. In line with other C-60-based nitroxide derivatives, the latter one gives a stable biradical anion upon one-electron reduction, and a metastable excited quartet state by visible light photoexcitation. Both species have characteristic EPR spectra. For the fulleroid derivative, the first reduction step is not chemically reversible and no excited state EPR signal is observed after LASER excitation, Electrochemical and spectroelectrochemical techniques indicate that fulleroid to methanofullerene conversion takes place by photoexcitation and, more interesting, upon injection of a single electron, contrary to the cases of other fulleroids so far reported.