Aims Adherence to the generally complex regimen of coumarin derivatives is vital in order to keep patients in the adequate I nternational N ormalized R atio range. Patients' beliefs about medicines are associated with the level of therapy adherence. Our first aim was to assess beliefs about coumarins. Secondly, we compared the beliefs about coumarins with the beliefs about other cardiovascular drugs. Methods The B eliefs about M edicines Q uestionnaire was used to assess medication beliefs. The questionnaire was completed by new users of coumarins indicated for venous thromboembolism or atrial fibrillation. A necessity score and a concerns score were calculated for all patients. The analyses were repeated for users of antihypertensive drugs or statins (not using coumarins). Results Three hundred and twenty patients were included in the analysis of the beliefs about coumarins. The mean necessity score was 15.3, the concerns score 12.3 and the necessity–concerns differential 3.0. Patients with venous thromboembolism ( n = 71) had higher necessity scores than patients with atrial fibrillation ( n = 249; 16.8 vs . 14.9, P < 0.001). The mean necessity score in 493 users of other cardiovascular drugs was 16.1, the concerns score 13.5 and the necessity–concerns differential 2.6. The necessity score was higher in chronic cardiovascular drug users ( n = 192) than in new users ( n = 301; 17.9 vs . 14.9, P < 0.001). Conclusions Coumarin users score higher on the necessity scale than on the concerns scale, which is also the case in users of other cardiovascular drugs. Patients with atrial fibrillation have a less positive attitude towards these drugs than patients with venous thromboembolism, and could therefore benefit more from specific attention.