Background: Depression in breast cancer (BCa) patients can reduce quality of life, relationships and treatment compliance, thus constituting a major target for cognitive behavioural (CBT) interventions. Although CBT treatments, which are built upon consideration of the roles of antecedents and consequences for depressive behaviour, are effective, the nature of those antecedents which trigger depression among BCa patients has received relatively little attention. Purpose: Hypotheses were (1) to determine if BCa patients were experiencing either or both of punishment type I and II and (2) to identify if these aspects of punishment were related to overall depression. Method: Two hundred fifty-three BCa patients completed a standardised depression scale, and data were factor analysed. Components were interpreted for their relationship to punishment type I or II. Results: Two major components emerged: (1) loss of previously available sources of personal or social reinforcement (i.e. punishment type II or negative punishment) and (2) behavioural, emotional and cognitive responses to those losses. These two components represent the total symptomatology of major depressive episode from DSM-IV-TR. Conclusion: These findings support the application of a functional analytic model of depression within CBT assessment and treatment procedures with BCa patients.