Decision-making is a process, consisted of a numerous mechanisms, which aim at ascribing a value to actions and environmental stimuli in a manner that allows making decisions and modifying them to maximize the probability of achieving significant goals. Most studies on the role of neurotransmitters in this process concern the dopaminergic and serotoninergic systems, interaction between both being especially relevant for the eventual action selection. The aim of the present work is to present the state-of-the-art, concerning the contribution of neurotransmitters to the decision-making process with special emphasis on pharmacological and genetic studies concerning the dopaminergic and serotoninergic systems.