Impulsiveness, the individual's tendency to respond quickly to a given stimulus without reflectivity and evaluation of the consequences, is considered as a determinant component of several psychiatric disorders. Dimensions of impulsiveness including nonplanning, motor impulsiveness, and cognitive impulsiveness could influence different aspects of depression and anxiety disorders. The main aim of the present study was to compare impulsiveness in patients with major depression, anxiety disorders, and normal individuals. This study demonstrates the differences of impulsivity among the three groups. A total of 224 individuals (87 depressed, 64 anxious, 73 normal) participated in this study, voluntarily. Following a psychiatric diagnosis of the psychological disorders, both the patient and normal groups were asked to complete the Barrat Impulsiveness Scale (BIS). Method of the present descriptive study was causal-comparative. Analysis of the data involved both descriptive and inferential statistics including means, standard deviations, and MANOVA. The results revealed that depressed patients reported significantly higher levels of motor impulsiveness and nonplanning than did anxious patients and normal individuals (p<0.001). Anxious patients reported higher levels of cognitive impulsiveness than did depressed patients as well as higher levels of cognitive impulsiveness and nonplanning than did normal individuals (p<0.001). Normal individuals reported lower levels of impulsiveness than did the two groups of depressed and anxious patients. It can be concluded that comparison of dimensions of impulsiveness in patients and normal individuals provides evidence of the possible impact of pathological impulsivity on the development and/or continuity of depression and anxiety disorders. The difference between levels and dimensions of impulsiveness of the two groups of depressed and anxious patients also could explain their differences in terms of the kind of psychological disorders.