Objectives: Existing findings on cancer patients' use of information sources were synthesized to (1) rank the most and least used information sources and the most helpful information sources and to (2) find the impact of patient demographics and situations on use of information sources. Methods: To synthesize results found across studies, a systematic review was conducted. Medline and CINAHL were searched to retrieve literature on cancer patients' information source use. The retrieved articles were carefully selected according to predetermined criteria, and several articles were eliminated in a systematic approach. Analysis: The twelve articles that met the criteria were systematically analysed by extracting data from articles and summarizing data for the purpose of synthesis to determine the meaning of findings on most used information sources, least used information sources, most helpful information sources, effect of patient characteristics on preference for an information source, and effect of patient situations on preference for an information source. Results: In descending order of use, health care professionals, medical pamphlets, and family and friends were most used information sources. Internet and support groups were least used. In descending order of helpfulness, books, health care professionals and medical pamphlets were found to be most helpful information sources. Younger patients used health care professionals and certain forms of written information sources more than older patients. Conclusions: The systematic review shows that many areas of cancer patients' information source use have been either neglected or barely analysed. An in-depth understanding of cancer patients' use of information sources and the characteristics in information sources they consider to be helpful is important for developing successful interventions to better inform patients.