A considerable proportion of Taiwanese people believe that Chinese medicine is superior for treating the cause of disease (curative therapy) whereas western medicine is mostly concerned with treating symptoms (symptomatic therapy). As a result, when illness arises, the combined use of both Chinese and western medicine is a common practice and referred to as pluralistic health-seeking behaviour. The purpose of this cross-sectional study was to explore the relationship between beliefs of superiority of western or Chinese medicine, utilisation of therapy and glycaemic control in patients with diabetes from outpatient departments. The study was conducted between 20 December 2005 and 20 January 2006. We approached 176 patients consecutively, and 151 (85.8%) completed the survey. Seventy-nine patients with diabetes from a municipal Chinese medicine hospital and 72 patients from a near by western medicine hospital in southern Taiwan were recruited. Participants were asked to fill in a structured questionnaire. For those who could not fill in the questionnaire, interviews were conducted. Sixty-four participants took western medicine (42.4%), 65 people (43.0%) used the combination of western and Chinese medicine and 22 (14.6%) used Chinese medicine only. Beliefs about the superiority of Chinese versus western medicine were associated with the patients’ utilisation of those therapies. Patients using a combination of Chinese and western medicine had significantly better glycaemic control than patients using Chinese medicine alone. Further research is needed to clarify whether better glycaemic control was the result of the combined therapy, a higher motivation for self-care or both. Nevertheless, a combination of traditional and western medicine plays an important role and should not be ignored in controlling diabetes. However, the cost-effectiveness of such a plural therapy needs to be investigated.