The pore-size distribution of a series of pitch-based activated carbon fiber samples (A5, A10, A15, and A20) has been determined from the nitrogen adsorption isotherms at 77 K, with the nonlocal density functional theory (DFT), the Dubinin-Stoeckli (DS) method, and the subtracting pore effect (SPE) method using the high-resolution as plot. The pore-size distributions of all the samples from. DFT show a distinguishable peak at small pore widths around 0.6 nm and a broad peak at bigger micropore size. The mean pore widths obtained from DFT and DS methods are similar for samples whose pores are narrow and different for wider ones. The use of the SPE method shows that the mean pore widths are slightly smaller than those obtained by DFT and DS methods.