The present study aimed to uncover the neural activity associated with specific in-group and out-group word related stimuli, to examine the neuroanatomical basis of group membership concept representation, and investigate to what extent neural processes represent 'in-group' differently from 'out-group'. Participants' brain activity was measured with functional MRI while they had to categorize social, in-group and out-group words and non-social, living and non-living words. The results showed that a network of brain regions previously identified as the 'social brain', including the cortical midline structures, tempo-parietal junction and the anterior temporal gyrus showed enhanced activation for social words versus non-social words. Crucially, the processing of in-group words compared to the out-group words activated a specific network including the ventral medial prefrontal and anterior and dorsal cingulate cortex. These regions correspond to a neural network previously identified as the 'personal self'. Our results suggest that the 'social' and 'personal self' are closely related and that we derive our self image from the groups we belong to.