OBJECTIVE: To determine the use of alternative diets and other alternative treatments in 2002 compared to 1999. DESIGN: Descriptive, questionnaire. METHOD: During the period 13-26 May 2002 a survey was held among all patients visiting the outpatient clinic of the Netherlands Cancer Institute/Antoni van Leeuwenhoek hospital, Amsterdam, the Netherlands. Patients were asked about their current and past use of alternative therapies, their reasons for using these therapies, the way they were informed about these therapies and the expenses involved. The data were compared with the results of a similar study during the period 15-19 March 1999. RESULTS: Of the 729 patients who fulfilled the inclusion criteria, 66 (9%) declined to participate in the study. Of the remaining 663 patients (average age 58.5 years; 28% male), 131 (20%) used an alternative therapy. Of these, 43 patients (7%) used an alternative diet, mainly the Houtsmuller diet, and 88 patients (13%) used a mixture of alternative therapies such as homeopathy, vitamins and herbs. In 1999, 131 patients (30%) used an alternative form of treatment, 51 (13%) of whom used a diet. Of the 43 users of diets in 2002, 11 (26%) believed that the diet would slow down the disease process; in 1999 this was 53% (27/51). Of the 131 users of alternative therapies in 2002, 55% had been made aware of the possibilities of alternative treatments via family and friends. Internet and TV played a minor role as a source of information. 33 (79%) of the diet users informed their physician or nurse about the use. The diet users spent an average of 170 euro per month on their diets. CONCLUSION: Both the percentage of cancer patients who used an alternative diet and the percentage of diet users who believed that a diet could affect the course of the disease were reduced by half compared to three years earlier.