With watchful waiting being increasingly considered as a reasonable alternative for curative treatments for some men with localised prostate cancer, this review aimed to explore the psychological impact of this treatment decision. The review showed that initially aspects of psychological wellbeing were negatively affected, possibly due to uncertainty around treatment choice and the ongoing experience of living with cancer. However over time men appeared to adjust and reported similar wellbeing scores to men in other treatment groups. Men with localised prostate cancer therefore need to be appropriately supported to manage the uncertainty related to watchful waiting. In continuation of the exploration of uncertainty in illness, seven people with a diagnosis of Mild Cognitive Impairment (MCI) were interviewed. MCI has an uncertain prognosis, whereby the cognitive changes may progress to dementia, remain stable or return to normal over time. The interviews were analysed using discourse analysis, in order to identify how the language used revealed societal views, shared meanings and positions taken by people. Three main discourses emerged. A discourse of ‘Not Knowing’ appeared for MCI. In the absence of a coherent discourse around MCI, participants positioned themselves between ‘Knowing’ about ageing and dying, and ‘Not Wanting to Know’ about dementia. How a diagnosis of MCI is shared and how further information is presented needs to be considered by clinicians, so that the person with a diagnosis of MCI can find a more supportive position, rather than finding themselves oscillating between discourses related to ageing and dying, and dementia. Contributions to theory development, future research and clinical practice were considered in respect to prostate cancer and MCI. The overlapping theme of uncertainty was discussed in relation to both conditions and how this can inform shared learning and clinical practice.