BACKGROUND: There is limited knowledge about patients' use of herbs and dietary supplements. In the current project we have studied this in Norwegian patients, also their sources of information, beliefs and attitudes. MATERIAL AND METHODS: A structured questionnaire was filled in anonymously by 149 patients (response rate 64%) with common cancer diagnoses. RESULTS AND INTERPRETATION: Of the patients, 56% used herbs and dietary supplements (average: 2.0 products per patient), while 36% used them for the cancer itself (average: 1.1 products each). Patients below 55 significant dominated the last-mentioned group. Among the patients, 53% believed that the products could strengthen their immune system, while 18% believed that they could contribute in their fight against cancer. However, as many as 62% answered "I don't know" to this question. As to what was true about the products, 86% found it difficult to judge, and 76% wanted information primarily from health personnel. One third had discussed the products with the doctor. Only 8% felt this to be very useful; hence communicating with cancer patients about herbs and dietary supplements can be a challenge, though at least it might help to discover side effects or interaction with the medicine given.