Breast cancer impacts the psychological well-being of women, leaving them at risk of developing
depression, anxiety, and other stress-related disorders. The Depression Anxiety Stress Scales (DASS21) is a widely used measure, although empirical evidence regarding its psychometric properties
in the breast cancer population is limited. The purpose of this study was to conduct an exhaustive
analysis of the psychometric properties of the DASS-21 in a sample of Spanish women diagnosed with
breast cancer. Participants were 289 breast cancer patients who completed the DASS-21 and other
questionnaires measuring life satisfaction, positive and negative afect, fourishing, perceived stress,
and breast cancer-specifc stressors. In terms of validity evidence based on the internal structure of
the DASS-21, adequate ft indices were obtained for the model based on three frst-order factors
(depression, anxiety, stress) and one second-order factor (general psychological distress). Reliability
coefcients (McDonald’s omega) ranged from .84 to .95. Validity evidence based on relationships with
other variables was also provided by moderate and strong correlations with well-being indicators
and stress measures. The results support the use of the DASS-21 for measuring general psychological
distress in the breast cancer context, where it may provide useful information for the design of
psychological interventions with patients.