The relationship between borderline personality disorder and bipolar disorder is a complex issue that there are contradictory opinions about that and emotional problems constitutes a main problem of these two forms of the disorder. The purpose of the study was to comparison of emotion regulation problems between patients with borderline personality disorder, bipolar I disorder and normal people. The Method of the research was casual- comparative design and 25 hospitalized patients with borderline personality disorder and 25 hospitalized patients with bipolar I disorder selected through convenience sampling at the Razi Psychiatry hospital of Tabriz, then in order to diagnosis of the patients used Structured Clinical Interview for DSM-II (SCID-II) & Structured Clinical Interview for DSM-Clinical Version (SCID-CV) and also to assessment of emotion regulation problems used Difficulties in Emotion Regulation Scale (DERS) . The data analyzed by ANOVA. The results show that there is a significant difference between two groups in terms of emotion regulation problems. Also, patients with borderline personality disorder gained high scores in difficulty in goal directed behavior, limited access to emotion regulation strategies and difficulty in impulse control subscales than other groups. There is also no difference between patients with BPD and BMD in the absence of emotional clarity, lack of emotional awareness & lack of emotional acceptance subscales, but both groups obtained higher scores than normal people. So, it can be concluded that emotion regulation problems among patients with BPD are more than in patients with BMD.