We used the Life Orientation Test-Revised (LOT-R) as a unidimensional scale to investigate the stability of dispositional optimism and compared the results with the stability of anxiety and depression. Five hundred and twelve women completed the LOT-R and the Hospital Anxiety and Depression scale before follow-up mammography and 4 weeks after receiving the result (breast cancer or not). This study shows that dispositional optimism is relatively stable and is not influenced by receiving a cancer diagnosis.