Background - Patients are increasingly using complementary therapies, often for chronic conditions. Asthma is the most common chronic condition in the UK. Previous research indicates that some asthma patients experience gaps in their NHS care. However, little attention has been given to how and why patients and parents of children with asthma use complementary therapies and the implications for NHS care.Methods - Qualitative study, comprising 50 semi-structured interviews with a purposeful sample of 22 adults and 28 children with asthma (plus a parent), recruited from a range of NHS and non-NHS settings in Bristol, England. Data analysis was thematic, drawing on the principles of constant comparison.Results - A range of complementary therapies were being used for asthma, most commonly Buteyko breathing and homeopathy. Most use took place outside of the NHS, comprising either self-treatment or consultation with private complementary therapists. Complementary therapies were usually used alongside not instead of conventional asthma treatment. A spectrum of complementary therapy users emerged, including "committed", "pragmatic" and "last resort" users. Motivating factors for complementary therapy use included concerns about conventional NHS care ("push factors") and attractive aspects of complementary therapies ("pull factors"). While participants were often uncertain whether therapies had directly helped their asthma, breathing techniques such as the Buteyko Method were most notably reported to enhance symptom control and enable reduction in medication. Across the range of therapies, the process of seeking and using complementary therapies seemed to help patients in two broad ways: it empowered them to take greater personal control over their condition rather than feel dependant on medication, and enabled exploration of a broader range of possible causes of their asthma than commonly discussed within NHS settings.Conclusion - Complementary therapy use reflects patients' and parents' underlying desire for greater self-care and need of opportunities to address some of their concerns regarding NHS asthma care. Self-management of chronic conditions is increasingly promoted within the NHS but with little attention to complementary therapy use as one strategy being used by patients and parents. With their desire for self-help, complementary therapy users are in many ways adopting the healthcare personas that current policies aim to encourage.