ABSTRACT This paper investigates from a phenomenological perspective the origins of self-illness ambiguity. Drawing on phenomenological theories of affectivity and selfhood, I argue that, as a phenomenon which concerns primarily the ‘personal self’, self-illness ambiguity is dependent on distinct alterations of affective background orientations. I start by illustrating how personhood is anchored in the experience of a specific set of non-intentional affects – i.e. moods or existential feelings – alterations of which are often present in mental ill-health. Also through the (...) exploration of the phenomenology of acute and long-term anxiety, I suggest that self-illness ambiguity originates in the presence of moods or existential feelings that are in tension with the ones that structure the person’s experience prior to the onset of the illness or when its symptoms are not experienced. More specifically, I claim that due to their ability to ‘block’ or ‘suspend’ some of the person’s affective and cognitive responses, such affective orientations may unsettle one’s self-defining evaluative perspective, leading to uncertainty and doubting about one’s personal self. (shrink)