Introduction: A significant aspect of person-centred care is the potential for patients to participate in their own health and healthcare in correspondence with their needs and resources, getting preference-based patient participation. A person living with hypertension is expected to partake in both self-care and prescribed treatment management. Yet, little is known what facilitates such engagement. This study illustrates their preference-based patient participation, evaluating the effects of a web-based support system via mobile phone. Methods:   A randomised controlled trial in which 949 patients across 31 primary healthcare centres completed the Patient Preferences for Patient Participation tool, the 4Ps, at three time points: baseline, following an 8-weeks intervention, and at 12 months. Results: At baseline, approximately half of the participants had a match between their preferences for and experiences of their participation in health and healthcare. Consequently, almost every second patient either had less provision for their engagement than favoured or had experiences of participation exceeding their conditions.  Most prominently sex, age and education were associated with different preferences for and experiences of participation, and the level of concordance thereof. The support system did not affect the preference-based patient participation long term, but the match between preferences and experiences seemed to improve regarding managing prescribed treatment and knowing what was done after 8-weeks in the intervention group.    Conclusion: With roughly half of the persons with hypertension not having had preference-based opportunities for participation there is a remaining need to facilitate healthcare professionals’ identification of patients’ preferences for participation in their care, and to let them serve as a guide in how communication, medical treatments and lifestyle modifications are planned and conducted. Further studies are planned on how more person-centred dialogues can be achieved in encounters in primary healthcare.