Humans use counterfactual thinking in order to evaluate their previous choices, comparing the actual outcome of a choice with what would have happened if they had chosen another action option. Two prototypical emotions resulting from such counterfactual evaluations are guilt and regret, both of which play an important role in regulating human choice behavior. Guilt is thought to refer specifically to social choices, while regret occurs for both individual and social choices. Here, we introduce an fMRI compatible new experimental paradigm to differentially induce guilt and regret under controlled conditions as a result of real decision. Behavioral data confirm that guilt but not regret specifically occurs in a social context (i.e. after harm for another person caused by own choices). On the neural level, initial results point to a critical involvement of different sub-regions within the prefrontal cortex in the processing of guilt vs. regret.