Women treated for breast cancer have shown cognitive deficits with reduced capacity to focus and concentrate or to direct attention. This study examined the relationship between cognitive function prior to any treatment for breast cancer and individual factors including age, education, menopausal status, chronic health problems, and distress. Women newly diagnosed with breast cancer (N=184), ages 27–86 years, were assessed with standardized attention tests, self-reports of effectiveness in cognitive functioning, and measures of distress at about 18 days before surgery. Measured performance on the cognitive tests was not significantly correlated to self-reports of effectiveness in cognitive functioning. Age, education, presence of a chronic health problem, and menopausal status, but not distress, were associated with performance on the cognitive tests. Only age and education, however, were significant (p<0.001) predictors of overall performance on the cognitive tests, when controlling covariates. In contrast, symptom and mood distress significantly (p<0.001) predicted perceptions of effectiveness in cognitive functioning. Thus, different factors were associated with measured performance versus self-reports of cognitive functioning. Individual factors that predispose to lowered effectiveness in cognitive functioning prior to treatment in women newly diagnosed with breast cancer are discussed. Copyright © 2004 John Wiley & Sons, Ltd.