Objective Identify the role of engaging people affected by cancer in service development in influencing healthcare professionals and service-users’ attitudes toward, and enactment of, engagement. Methods Focus group discussions with healthcare professionals and people affected by lung cancer, prior to and following an intervention where lung cancer teams were supported to engage with patients and family members. Results Staff and people affected by cancer who participated displayed more positive attitudes toward involvement than those who did not participate. Conclusion Progressing the involvement agenda requires the use of supported, small scale, projects where staff and patients/family members can develop their skills and knowledge of involvement. Practice implications Doing patient engagement work is a vital step toward changing attitudes and actions toward the involvement agenda.