The aim was to investigate the effect of web-based patient information on patients' satisfaction with care during an F-FDG PET/CT examination, their knowledge about the examination and the image quality, compared with standard care, and to explore the usage of and satisfaction with web-based information. One hundred-forty-eight patients were recruited between October 2015 and December 2016 and randomly assigned to Standard Care (SC) or an Intervention Group (IG). SC received information about the F-FDG PET/CT examination according to standard care and IG also received access to web-based information about the examination. A questionnaire was used to evaluate patient satisfaction, knowledge and discomfort and a blinded image quality assessment was conducted. The overall satisfaction was high in both IG and SC. The lowest satisfaction concerned the information about how the patients would receive the results about the PET/CT examination. More patients in IG than SC knew how the F-FDG PET/CT examination was conducted. Descriptive data suggest that image quality was slightly better in IG than SC, but there were no statistically significant differences between the groups regarding any of the outcomes. The recruitment encountered several obstacles leading to an insufficient power to detect differences. Also, only 54 of 75 patients (72%) in IG used the web-based information. However, those who used the web-based information were satisfied and found it helpful. Effects of web-based information need to be investigated in a larger sample of patients. Improved information before an F-FDG PET/CT examination may increase patient knowledge and help them to prepare and undergo the examination. It may also improve image quality. However, this needs to be investigated using image quality as the primary outcome. The results may be used to improve patient information and care and thereby optimise theF-FDG PET/CT examination procedure.