Predicting adsorption over a range of operating conditions and the improvement of the adsorbent itself are two important aspects that arise in the industrial application of adsorption. Both of these aspects can be addressed using molecular simulation techniques in conjunction with an appropriate model of the internal structure of the adsorbent. The internal structure of activated carbons is particularly difficult to model due to the fact that the structure is only locally crystalline and that most of the void volumes within the structure have length scales comparable to small molecules. This paper presents a systematic method to develop suitable models of the internal structure that are based on networks of regularly shaped model pores. Important aspects that are addressed include the realism and consistency of the resulting models. The method is illustrated using the adsorption of pure methane and ethane, and binary mixtures of these components, over a wide range of operating conditions onto four activated carbons.