This paper contributes to the growing recognition in Science and Technology Studies and medical sociology of the significant role of affect in scientific and clinical work. We show how feelings of fear and anxiety associated with dementia not only shape people’s experiences and responses to a diagnosis, but also shape the practices and processes through which assessments and diagnoses are accomplished. What emerges from our research, and provides a distinct contribution to this growing field of study, is the relationship between the uncertainties that pervade the diagnosis of memory problems and the various strategies and practices employed to care for, divert, restrict or manage affective relations. Furthermore, our ethnographic material illustrates the implications of this relationship: on the one hand, it provides opportunities for care work through ‘tinkering’ with diagnostic technologies and extending and opening out diagnostic categories, while on the other, it can form part of healthcare practitioners’ disposal work, restricting opportunities for alternative meanings of dementia to endure.