The experiments described in this thesis aim at investigating the influence of appetitive motivation on decision making. The single experiments address distinct components of decision making. All experiments include some form of manipulations of participants' desire to eat. We analyzed the effects of such manipulations on participants' behavioral responses and the responses of their neural systems. Experiment 1 investigated the dependence of cognitive flexibility on motivational factors. It showed that cognitive flexibility was affected by either hunger or desire. The results demonstrate that changes in motivational state can produce altered cognitive flexibility levels and point to a psychological interface between motivation and cognition. Experiment 2 targeted the neural basis of motivational modulations identified in experiment 1 . It showed differences between the activations associated with the cognitive processes, depending on participants' hunger state. The results show that motivation can modulate prefrontal activity associated with cognitive processes. Experiment 3 examined the influence of motivational state on the representation of incentive value. Activity in the amygdala was consistent with the representation of attractiveness, while the orbitofrontal cortex showed a response pattern indicating integration of incentive value with hunger state. Experiment 4 targeted the selection of an option among others. Choice guided by affective processes activated the insula, anterior temporal cortex and the medial OFC, consistent with involvement of the insula in gustatory and interoceptive perception processes and of the anterior temporal cortex in affective and mnemonic processing. It also dissociated the role of medial and lateral orbitofrontal cortex in choice. Thus, the results of the experiments show that the cognitive and motivational systems are dependent on each other. The understanding of the interactions of cognition and motivation will be crucial for the understanding of decision making.