The present study defined cancer information overload (CIO) as an aversive disposition wherein a person is confused and overwhelmed by cancer information, which occurs when he or she fails to effectively categorize new information due to a lack of resources for effective learning. Based on the definition and informed by previous studies on information overload and the cognitive mediation model, we hypothesized that low ability and motivation to process cancer information would lead to CIO. We used education level and trait anxiety as factors related to ability. Cancer history and the use of active media channels (such as the Internet and print media) were adopted as motivational factors. Four samples (three from the United States and one from South Korea) were used to explore the relationship between ability/motivation and CIO. Among them, only Sample 4 participants answered questions about stomach cancer, and other participants were asked about cancer in general. In all four samples, trait anxiety was positively associated with CIO. Health information use from active media channels (print or the Internet) was negatively associated with CIO in three samples. The associations between family history and CIO, and between education and CIO, were found in two samples. In short, the present study demonstrated that CIO partly depends on individual ability and motivation, thereby showing that CIO is influenced by personal characteristics as well as environmental factors.