Background: The increasing demand for complementary medicine indicates a change in attitudes regarding treatment understanding. Objectives: To investigate the role of attitudes in treatment motivation. (1) Can the study sample be subdivided into homogenous groups as regards attitudes toward complementary treatment? (2) How do these groups relate to motivational variables? Patients and Methods: Four questionnaires on motivation and attitudes were administered to 203 patients of two clinics for complementary medicine. Results were interpreted following Petry's motivational process model that distinguishes treatment disposition, preparedness for treatment and treatment activity. Results: According to a cluster analysis, 3 patient groups could be identified: `Not- convinced' patients (cluster 1, n = 24) demonstrated little conviction regarding any aspect of complementary treatment. `Convinced' patients (cluster 2, n = 103) showed a high degree of agreement on all three scales, being highest on `Role of patient'. `Partially- convinced' patients (cluster 3, n = 70) also evaluated `Role of patient' highest, but aspects of the `Physician- patient relationship' and the `Treatment method' were only partly regarded as important. In all clusters, the pragmatic motive of treatment acceptance was central for the treatment choice, but was highest in cluster 2. As compared to cluster 1, a complementary treatment understanding was higher in patients of clusters 2 and 3 ( highest in cluster 2). Discussion: Even if the pragmatic treatment motivation was high in all groups, the central role of treatment attitudes in the motivational process could be verified. Despite differing attitude structures, a majority of patients displayed a complementary treatment comprehension.