BackgroundIn the information era, patients can easily be misled by inaccurate internet content, thus making not well-informed decisions about medical issues. Adenoid hypertrophy, one of the most common causes of chronic upper airway obstruction in children and adolescents, may lead to serious complications, including sleep apnea and craniofacial change. There have been no critical studies about the quality of websites on adenoid hypertrophy, posing a challenge for users without a medical background to determine which website offers more reliable information. Moreover, the blockage of access to internet search tools such as Google, Yahoo, and others has created an isolated internet environment for the enormous user population in mainland China. Differences in internet legislation, the commercial environment, and culture are also likely to result in varied quality of online health information inside and outside mainland China. To date, no study has compared the quality difference between mainland Chinese and English websites.ObjectiveThe aims of this study were to (1) analyze the quality of websites about adenoid hypertrophy accessible by patients, (2) investigate the quality differences between Chinese and English websites, (3) determine which type of website (eg, government-sponsored, health care provider) is more reliable in terms of medical information, and (4) determine whether the blockage of foreign websites is hindering users’ accessibility to better-quality websites in mainland China.MethodsThe first 100 websites (excluding advertisements) displayed on the top three search engines worldwide and in mainland China for the key search term “enlarged adenoids” were collected as the data source. The websites were evaluated based on accessibility, accountability, interactivity, structure, and content quality (accuracy, content coverage, and objectivity). Cohen κ was calculated, and one-way ANOVA and the Kruskal-Wallis test were performed to compare the results between groups and subgroups.ResultsThe mean score for the content quality of English websites was significantly higher than that of Chinese websites (6.16 vs 4.94,P=.03 for Google, Bing, and Yahoo; 6.16 vs 4.16,P<.001 for Baidu, Sougou, and Bing China). Chinese users who are not influenced by the Internet Censorship System are more likely to access higher-quality online medical information (4.94 vs 4.16,P=.02). In within-group Student-Newman-Keulsqposthoc analysis, professional organization and government-sponsored websites were generally of better quality than other websites for both Chinese and English websites (P<.05).ConclusionsGenerally, the English websites on adenoid hypertrophy are of better quality than Chinese websites; thus, Chinese users residing outside of the Chinese mainland are less influenced by inaccurate online medical information.