PURPOSE: To determine the influence and impact of [F]- fluorodeoxyglucose positron emission tomography (FDG PET) in Denmark. METHODS: A standardized questionnaire was sent to the referring physicians of 743 consecutive cases between January 2000 and December 2001. The questionnaire was designed to determine whether and how the results of the FDG PET imaging changed patient management. RESULTS: The response rate was 71% (524 responded). The distribution of all responding physicians included 26 different specialities. The majority were from haematology (23%), oncology (20%), plastic surgery (17%) and neurology (10%). The primary diagnoses at referral was in the field of oncology (94%), with lymphoma (24%), melanomas (20%), unknown primary neoplasms (13%), nervous system neoplasms (9%), lung cancer (6%) and cancer of the digestive system (4%). FDG PET imaging resulted in a change in the patients' management in 224 cases (43%). Of these, surgery was affected in 88 cases. Chemotherapy was affected in 71 cases and radiation therapy in 54 cases. In patients where the intended plan of management was not changed, 78% of the physicians stated that FDG PET was nevertheless clinically helpful; for example confirmed the diagnosis, helped staging, changed treatment plan or confirmed treatment of choice. Physicians indicated a general satisfaction with FDG PET imaging in 86% of the cases. CONCLUSION: This survey-based study indicates that FDG PET imaging has a major impact on patient management, contributing to changes in management in 43% of cases. The present study also demonstrates that referring physicians are generally satisfied with FDG PET imaging in 86% of the cases.