PURPOSE Electronic patient-reported outcome measures (ePROMs) are digitalized health questionnaires used to gauge patients' subjective experience of health and disease. They are becoming prevalent in cancer care and have been linked to a host of benefits including improved survival. MyChristie-MyHealth is the ePROM established at the Christie NHS Foundation Trust in 2019. We conducted an evaluation of this service to understand user experiences, as well as strategies to improve its functioning. METHODS Data collection: Patients who had opted never to complete MyChristie-MyHealth (n = 87), and those who had completed at least one (n = 87) were identified. Demographic data included age, sex, ethnicity, postcode, diagnosis, treatment intent, and trial status. Semistructured interviews were held with noncompleters (n = 30) and completers (n = 31) of MyChristie-MyHealth, as well as clinician users (n = 6), covering themes such as accessibility, acceptability and usefulness, and open discourse on ways in which the service could be improved. RESULTS Noncompleters of MyChristie-MyHealth were older (median age 72 v 66 years, P = .005), receiving treatment with curative rather than palliative intent (odds ratio [OR], 1.45; P = .045), and less likely to be enrolled on a clinical trial (OR, 0.531; P = .011). They were less likely to own a smartphone (33% v 97%) or have reliable Internet access (45% v 100%). Satisfaction with MyChristie-MyHealth was high in both groups: 93% (n = 29) of completers and 87% (n = 26) noncompleters felt generally happy to complete. Completers of MyChristie-MyHealth wanted their results to be acknowledged by their clinicians. Clinicians wanted results to be displayed in a more user-friendly way. CONCLUSION We have broadly characterized noncompleters of the Christie ePROM to identify those in need of extra support or encouragement in the clinic. An action plan resulting from this review has been compiled and will inform the future development of MyChristie-MyHealth.