Impulsivity is central to several psychopathological states in adolescence. However, there is little consensus concerning the definition of impulsivity and its core dimensions. In response to this lack of consensus, Whiteside and Lynam (2001) have developed Impulsive Behavior Scale, which is able to distinguish 4 dimensions of impulsivity in adults: Urgency, lack of Premeditation, lack of Perseverance, and Sensation seeking. The aim of this study was investigating the reliability, validity and factor structure of the UPPS scale on 484 Iranian undergraduate students (190 male, 294 female). The item total correlations and factor analysis of questionnaire items showed that four items have insignificant correlations coefficients and weak factor loadings. The Cronbach's alpha coefficient of 42 item questionnaire was 0.796. Principal component analysis, using a varimax rotation, resulted in the following components: Urgency, Lack of premeditation, Lack of preservance, Sensation seeking. Goodness-of-fit indices of confirmatory factor analysis confirmed the four extracted factors, but the secondorder factor analysis indicated that the three factor model is better than the four factor model, excluding sensation seeking.