Background: In response to the escalating burden of chronic illness in Australia, recent health policies have emphasised the promotion of patient self-management and better preventive care. A notable omission from these policies is the acknowledgment that patients with chronic illness tend to have co-morbid conditions. Our objectives were: to identify the common challenges comorbidity poses to patients and carers in their experiences of self-management; to detail the views and perceptions of health professionals about these challenges; and to discuss policy options to improve health care for people with co-morbid chronic illness. The method included semistructured interviews and focus groups with 129 purposively sampled participants. Participants were people with Type 2 diabetes, chronic obstructive pulmonary disease and/or chronic heart failure as well as carers and health care professionals. Content analysis of the interview data was conducted using NVivo7 software. Results: Patients and their carers found co-morbidity influenced their capacity to manage chronic illness in three ways. First, co-morbidity created barriers to patients acting on risk factors; second, it complicated the process of recognising the early symptoms of deterioration of each condition, and third, it complicated their capacity to manage medication. Conclusion: Findings highlight challenges that patients with multiple chronic conditions face in relation to preventive care and self-management. Future clinical policy initiatives need to move away from single illness orientation toward strategies that meet the needs of people with comorbid conditions and strengthen their capacity to self-manage. These patients will benefit directly from specialised education and services that cater to the needs of people with clusters of comorbidities.