A direct and fast voltammetric method of determination of 2,8-dihydroxyadenine (2,8-DHA), with a novel nanostructured carbon fiber sensor (CFS), is revealed in this work. To achieve high sensitivity required in biological determinations, before the determination of 2,8-DHA, carbon fiber sensors were activated by electrochemical pretreatment method. The electrochemical activation process generates a nanostructured carbon fiber surface, which is stable. The high stability of the active surface, and the high reproducibility of the activation process, leads to reproducible and sensitive fast scan voltammetric (