Rationale, aims and objectivesThe nature of the relationship between bipolar disorder and borderline personality disorder has been an intense field of debate in the last two decades. Current diagnostic classifications approach this complex phenomenon using syndromatic definitions based on presence or absence of a restricted set of signs or symptoms that have demonstrated low specificity. One of the several utilities of the phenomenological method in psychiatry is to complement the clinical panorama, helping in the process of identifying potential differences between two separated clinical syndromes. The main objective of this publication is to explore one particular clinical difference between these two conditions - that is, the experience of self-continuity and time perception. Methodsthe argument explored in this paper is based on previous second-person or phenomenological accounts of sufferers of both conditions. Results and ConclusionsWhereas borderline personality disorder patients tend to experience only the present moment, referring frequent difficulties of drawing experiences of the past in order to determine their own future, bipolar disorder patients are constantly worried about the contradictions in their past experiences and the latent risk of losing control of themselves in future episodes of their disease. This contrast should be, however, corroborated in future research comparing directly the two groups in terms of the continuity of the self and their temporal structures.