Bipolar disorder and borderline personality have an impact on patients' life regarding to the symptomatology and the quality of life. Both disorders appear to have clinical similarities which do not facilitate the diagnosis. Indeed, the affective dimensions, both lability and intensity and as well as impulsivity, make clinical distinction difficult between these two pathologies. Through this review, we have described affective and impulsive dimensions for each disorder in a first time and we have tried to highlight the differences, concerning affectivity and impulsivity, between bipolar disorder and borderline personality disorder to refine the therapeutic treatment of both disorders in a second time. The main differences between bipolar disorder and borderline personality disorder concern the fact that patients with borderline personality disorder seem to have a higher level of affective intensity and impulsivity. Moreover, bipolar patients have fluctuations between "Anxiety" and "Depression" in terms of affective lability whereas borderline patients fluctuate between "Euthymia", "Depression" and "Elation".