Engineering the internal structure and chemical composition of nanomaterials in a cost-effective way has been challenging, especially for enhancing their performance for a given application. Herein, we report a general strategy to fabricate hollow nanostructures of ruthenium-based binary or ternary oxides via a galvanic replacement process together with a subsequent thermal treatment. In particular, the as-prepared NiO-RuO2 hollow nanostructures loaded on carbon nanotubes (hNiO-RuO2/CNT) with RuO2 mass ratio at 19.6% for a supercapacitor adopting the KOH electrolyte exhibit high specific capacitances of 740 F g(-1) at a constant current density of 1 A g(-1) with good cycle stability. The specific capacitance for hNiO-RuO2/CNT electrodes maintains 638.4 F g(-1) at a current density of 5 A g(-1). This simple approach may shed some light on the way for making a wide range of metal oxides with tunable nanostructures and compositions for a variety of applications.