It is demonstrated that the performances of supercapacitors are often affected by the electrochemical interface in their electrodes. In this work, the electrochemical interface in carbon nanofiber (CNF)/carbon nanotube (CNT) hierarchical composites was well optimized by tuning the diameters of electrospun CNF skeletons and the densities/lengths of CNT hierarchies. The optimized CNF/CNT composites decorated with MnO2 exhibited high specific capacitance (similar to 631.0 F g(-1) at current density of 0.9 A g(-1)) and excellent cycling stability (over 95% after 1500 cycles). Moreover, the assembled symmetric supercapacitors show a high flexibility and an excellent dynamic cycling stability, outputting the maximum energy density of 19.11 W h kg(-1) and the maximum power density reaching 25,000 W kg(-1). This research confirmed that the performances of the electrodes based on CNF/CNT hierarchical composites and their counterpart devices can be well tuned by tailoring their three-dimensional electrochemical interface. (C) 2016 Elsevier Ltd. All rights reserved.