Context <p>Graphene is considered to be a wonder material with widespread applications. However, its potential for recovering methylated DNA bases has not yet been explored. DNA methylation is implicated in the development of several health issues such as mutation, ageing, cancer and neurodegenerative diseases. The cytotoxic N7-methylated guanine (N7mG) is the most abundantly occurring methylated DNA lesion. Therefore, we have theoretically investigated the reactions of pristine, heteroatom-doped and functionalized graphene with N7mG cation with an intention to understand the efficacy of graphene in repairing this lesion. The epoxide- and thioepoxide-functionalized graphene can effectively restore guanine from the N7mG cation in both gas and aqueous phases. Pristine and BN-codoped graphene are, however, found to be unsuitable for this work. Thus, the present study offers valuable insights into how graphene may help in repairing N7mG and other modified DNA bases.</p> Methods <p>The calculations related to energetics, structural optimizations, natural bond orbitals (NBOs) and DOS were performed using two functionals (M06-2X and wB97X-D) of density functional theory (DFT) in association with 6-31G* and 6-31+G** basis sets, as available in the Gaussian 09 quantum chemistry code. The IEF-PCM was used for the aqueous phase calculations. The CHelpG charges were used for charge transfer analysis.</p>