Background: The NHS Health Check is a national cardiovascular disease prevention programme. There is a lack of evidence on how health checks are conducted, how cardiovascular disease risk is communicated to foster risk-reducing intentions or behaviour, and the impact on communication of using different cardiovascular disease risk calculators. Objectives: RIsk COmmunication in Health Check (RICO) study aimed to explore practitioner and patient understanding of cardiovascular disease risk, the associated advice or treatment offered by the practitioner, and the response of the patients in health checks supported by either the QRISK®2 or the JBS3 lifetime risk calculator. Design: This was a qualitative study with quantitative process evaluation. Setting: Twelve general practices in the West Midlands of England, stratified on deprivation of the local area (bottom 50% vs. top 50%), and with matched pairs randomly allocated to use QRISK2 or JBS3 during health checks. Participants: A total of 173 patients eligible for NHS Health Check and 15 practitioners. Interventions: The health check was delivered using either the QRISK2 10-year risk calculator (usual practice) or the JBS3 lifetime risk calculator, with heart age, event-free survival age and risk score manipulation (intervention). Results: Video-recorded health checks were analysed quantitatively (n = 173; JBS3, n = 100; QRISK2, n = 73) and qualitatively (n = 128; n = 64 per group), and video-stimulated recall interviews were undertaken with 40 patients and 15 practitioners, with 10 in-depth case studies. The duration of the health check varied (6.8–38 minutes), but most health checks were short (60% lasting