Impulse control is an important aspect of self-regulation. However, the definition and measurement of impulsivity is still a matter of debate. The main objective of this paper is to describe a multi-factorial model of impulsivity taking into account its emotional, cognitive and motivational components. Whiteside and Lynam  distinguished four facets of impulsivity: Urgency, lack of Premeditation, lack of Perseverance and Sensation Seeking. We will discuss the psychological and brain mechanisms involved in these facets and also propose tasks to assess each one.