The Internet is now more widely used than before by psychiatric patients and their families to search for medical conditions and treatments. To our knowledge, no study has addressed the quality and readability of online information about electroconvulsive therapy (ECT). We aimed to examine the quality and readability of English-language Internet information related to ECT. An advanced search of Internet Web sites containing information about ECT was conducted by using the search term "ECT or electroconvulsive therapy." The resulting Web sites were categorized into 1 of 3 categories (commercial, nonprofit, or professional organizations). Their quality was evaluated using Health on the Net code certification, the Journal of the American Medical Association (JAMA) benchmark criteria, and the DISCERN tool. The readability of the Web sites was assessed using the Flesch Reading Ease, Flesch-Kincaid Grade Level Formula, Simple Measure of Gobbledygook, and Gunning Fog indexes. A total of 86 Web sites were included in the analysis. Of all these Web sites, 18 (20.9%) had a Health on the Net code certificate, and 16 (18.6%) were accepted as high quality (JAMA total score ≥3). The commercial Web sites had significantly lower DISCERN and JAMA benchmark scores compared with the other Web sites. A total of 30.23% of all the Web sites reached the recommended readability level (Flesch-Kincaid Grade Level Formula ≤ 8). Moreover, only 4 scored at the grade 5 to 6 reading level, which is considered ideal for patient educational materials. Our study indicates that both the quality and readability of online information about ECT are not at the desired level. Physicians, patients, and their families should consider this failure in relation to online information about ECT. In addition, Web site creators and health authorities should be aware of their responsibilities for providing quality and readable health information to the public.