The self-reporting of cancer history is becoming increasingly important, as it frequently guides medical decision-making. We studied the accuracy of personal cancer history using a self-administered questionnaire, comparing the results with the Tumor Registry at our institution. Among 39,662 records, we identified 3614 women with a single cancer in the Tumor Registry who reported none or one cancer on their questionnaire. The sensitivity in self-reporting cancers was 85.7%, ranging from 92.1% for breast cancer to 42.9% for leukemia. The accuracy for breast cancer and Hodgkin's Lymphoma was significantly better than other cancers (p=0.00027, CI: 1.4-3.88). Analysis of patient's characteristics showed that Caucasians reported breast cancer more accurately than Asian/Pacific Islanders (p=0.008), and those with Jewish ancestry more accurately than non-Jewish (p=0.0435). These results will help us to improve data collection and thus improve medical decision-making.