An fMRI study was conducted to explore the neural basis of altruism in social decision-making. The participants were confronted with a non-monetary version of the Prisoner's Di-lemma which is one of the earliest games developed in game theory. They could make a choice between that which would lead to their own benefit, but to the harm of another person, and one which denies ones own benefit but would be in the interest of the other person. A comparison between these social problems and a set of matched non-social problems (in which no other person was involved) revealed that a complex neural network of cortical and sub-cortical brain areas is involved in making altruistic or selfish decisions. The findings indicate that the decision to behave altruistically relies on the interactions between cognitive control processes in prefrontal cortex and emotional control processes in the amygdala.