The gap in cancer information seeking between high-socioeconomic-status (high-SES) cancer patients and low-SES cancer patients deserves serious attention, considering the importance of information and knowledge in cancer control. We thus explored the association of SES, as measured by education, with cancer patients' overall cancer information seeking, and with seeking from each source (i.e., the Internet, mass media, medical sources, and nonmedical interpersonal sources) and across two topic categories (i.e., treatment, quality of life). We then asked whether the effect of education on treatment information seeking is reduced among those who are particularly motivated to control treatment choices. We conducted a survey with breast, prostate, and colon cancer patients diagnosed in 2005 (n = 2,013), who were randomly drawn from the Pennsylvania Cancer Registry in the fall of 2006. We found that education was more strongly associated with Internet use than with the use of other sources regardless of topics. Also, when information was sought from mass media, education had a greater association with treatment information seeking than with quality-of-life information seeking. Preference for active participation in treatment decision making, however, did not moderate the effect of education on treatment information seeking. The implications of these findings for public health research and cancer patient education were discussed.