Background: Current healthcare policy advocates patient participation in treatment decision making. However, in asthma there is little evidence regarding patients' views on such involvement. This study explored the preferred and perceived level of involvement in treatment decisions, rationales for role preference, perceived facilitators of/barriers to involvement, and the interrelationship of role preference and demographic variables in a sample of patients with asthma. Methods: A cross sectional survey was performed of 230 adults with clinician diagnosed asthma from 10 primary care sites and one specialist respiratory centre in north-west England. Preferred role in treatment decisions was assessed using the Control Preferences Scale. Results: Fifty five (23.9%) preferred an active role, 82 (35.7%) a collaborative role, and 93 (40.4%) a passive role; 19 (8.2%) perceived their role as active compared with 45 (19.6%) collaborative and 166 (72.2%) passive. Only 33.5% (n = 77) of respondents attained their most preferred role; 55.2% (n = 127) were less involved than they preferred. Patient related, professional related, and organisational factors, especially quality and duration of consultations, facilitated or hampered involvement. Role preferences were not strongly associated with demographic variables or asthma severity. Conclusions: This study in patients with asthma highlights the fact that there is a need for professional and patient education regarding partnership working, skilful communication, and innovative approaches to service delivery.