This study examined among recently diagnosed breast and prostate cancer survivors (N = 678) associations between worry about a future diagnosis of heart disease or cancer and hypothetical and actual adherence to exercise and dietary guidelines. Greater worry about future illness was reported under the hypothetical scenario of nonadherence to guidelines relative to the scenario of adherence. Worry about potential heart disease was associated with actual adherence to guidelines, whereas worry about a potential cancer diagnosis was not. Findings suggest that the motivational properties of worry should be considered when developing interventions to reduce heart disease risk among cancer survivors. Copyright © 2008 SAGE Publications.