Abstract: Ultrafine hierarchically porous carbon fibers (HPCFs) were produced by electrospinning from phenolic resin and Fe(acetylacetonate)₃, carbonization under an NH₃ atmosphere and HCl/water leaching to remove the Fe species. Their adsorption performance for ethanol and acetone and their pore structure were compared with fibers produced from polyacrylonitrile (PAN) and Fe(acetylacetonate)₃ (HPCFs(PAN)), and phenolic resin without the Fe(acetylacetonate)₃ addition (PCFs). Results indicate that HPCFs and HPCFs(PAN) are hierarchically porous with abundant micropores and mesopores while PCFs are dominantly microporous. The addition of Fe(acetylacetonate)₃ promotes graphitization. The hierarchical pore structure increases the uptake of both ethanol and acetone vapors at high pressures by multilayer adsorption while the microporous structure contributes to the uptake at low pressures by monolayer adsorption. The highest ethanol and acetone adsorption uptakes were found for the HPCFs, and are 7.55 and 12.56 mmol g^-1 at 25℃, respectively. Superiority of phenolic resin to PAN as the carbon precursor is demonstrated. The freestanding characteristic of the ultrafine carbon fibers as a result of their electrospining is advantageous as an adsorbent for the removal of volatile organic compounds.