Pore size-controlled carbon aerogels (CA_X) are prepared from two starting materials: resorcinol and formaldehyde. Carbon aerogels with different pore sizes are successfully obtained by simply varying the polymerization time (X) in the polycondensation of resorcinol and formaldehyde. Pore sizes of the carbon aerogels monotonically increase with increasing polymerization time. The pore size of the carbon aerogel plays an important role in determining its electrochemical behavior (i.e., specific capacitance in EDLC) especially at high current density. A sufficiently large pore size in a carbon aerogel is required for easy transport of electrolyte ions, and these types of carbon aerogels provide excellent electrochemical performance as an EDLC electrode. CA_20, which was polymerized for the longest time, have the largest pore size and the largest pore volume. CA_20 exhibit the highest specific capacitance due to facile electrolyte ion transport. As a result, design of carbon aerogels with a sufficiently large pore size while maintaining a high specific surface area is very important for developing carbon aerogels for use in EDLC electrodes. In addition, we propose a schematic reaction pathway for the preparation of carbon aerogels in ambient conditions from resorcinol and formaldehyde using a base catalyst based on the characterization results. (C) 2016 Elsevier B.V. All rights reserved.