The ability to determine whether a pore size distribution can be fitted to a given set of experimental data is relevant to the development of pore network models of the internal structure of activated carbons and other amorphous adsorbents. A closely related problem that arises when pore size distributions can be fitted to a given set of data is to determine suitable methods to calculate reliable, stable, and representative pore size distributions. This paper addresses both of these issues by presenting a procedure to determine whether a pore size distribution based on a specified model pore geometry can be fitted to a set of experimental data and then using this procedure, in conjunction with regularization techniques that stabilize the calculations, to determine statistically significant pore size distributions. This approach has been demonstrated using the adsorption of methane at 308 K onto BPL-activated carbon as a case study.