Objective: To verify whether the Credibility Indicator is able to evaluate the quality of websites. Method: This is a descriptive cross-sectional study of websites on diet and anorexia ⁄ bulimia, using searches on Google to access the study population. Quality was studied using 22 variables selected by consolidating international proposals. In addition, eight variables belonging to the Credibility Indicator were also studied. Results: Three hundred and fifty four homepages relating to diet and 366 homepages relating to anorexia ⁄ bulimia were evaluated. None of the websites met all of the quality criteria; neither did any website satisfy all of the Credibility Indicators. A positive correlation was observed between fulfilment of the Quality items and the Credibility Indicator (R = 0.72; P < 0.001). Significant differences were found in the fulfilment of the Total Quality variables between the websites that had these variables and those that did not (t-test = )9.91, P < 0.001).Conclusions: The quality of websites covering issues of diet and anorexia ⁄ bulimia is still poor. The Credibility Indicator is a useful aid when determining the quality of a website. It is evident that identifying authorship and affiliation is an important factor in predicting the quality of the information.Keywords: anorexia nervosa, bulimia nervosa, diet, communication health, information dissemination, internet, quality control. Key messages Implications for Practice• The need to evaluate the abundance of health-related information available on the Internet.• The poor quality of websites related to diet and anorexia ⁄ bulimia.• Knowing the authorship and affiliation of the website, regardless whether the website is specifically related to diet or anorexia ⁄ bulimia, is an important factor in predicting the quality of the information.• The Credibility Indicator is a useful aid when determining the quality of a website.• It is useful to note whether the website benefits from quality accreditation certification from organizations such as HONcode and Web Médica Acreditada, which would provide the necessary confidence in the website content. Implications for Policy• Those responsible for health-related websites should consider the quality criteria set out by the main international health agencies.• Evaluating the quality of health-related websites is necessary.• It may be necessary to insist on the construction of Quality Indicators, which are readily understood, to evaluate effectively the many health-related websites.