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In this work, we explain the removal of harmful volatile organic compounds (VOCs) by adsorbing them on activated carbon fibres (ACFs). For this purpose, we prepared a significant number of ACFs with different surface chemistries and porosity developments, and analyzed the effect of these two variables on VOC adsorption. Our results showed that at low concentrations (around 1000 ppmv), pore size distribution (PSD) is the main parameter that controls the removal of VOC. Therefore, a narrow PSD with a mean pore size between 0.8 and 1.0 nm is most appropriate to achieve high VOC adsorption capacities at these concentrations. However, at lower concentrations (P/P 0 < 10 −2 ), VOC adsorption capacity depends on different adsorbent properties (not only on the PSD but also on the surface chemistry) and on the polarity of the VOC. For this reason, the selection of the activating agent (CO 2 or H 2 O) has an important influence on the adsorption process depending on the polarity of the organic compound to be adsorbed. Thus, for example, steam activation would be better for the adsorption of polar compounds because of the higher amount of surface oxygenated groups developed from the steam activation.