The aim of this study was to assess the quality and safety of the information presented on the Internet about medicinal herbs for cancer. Two hundred relevant websites were initially selected from a process using 10 search engines and the keywords ‘herbs’ and ‘cancer’, and 43 sites met all inclusion criteria. Most sites had low quality in a number of indicators, including accuracy of information, revealing sources of information, biased presentation of information or regularity of updates. The mean score for quality was 22.12 out of a maximum score of 50. The mean safety score was 13.26 out of a maximum score of 30. Commercial sites had the most inaccurate or misleading information, emphasising only the positive aspects of the use of herbs, with little or no evidence. Seven percent of the sites discouraged the use of conventional medicine.