Objective This study addresses the meanings women with breast cancer attach to their illness within a cognitive‐developmental framework. The aim of the present study was twofold: (i) to identify the content of women's meanings in five domains of breast cancer representation (identity, causes, consequences, timeline and controllability), and (ii) to verify if those meanings can be classified developmentally and propose a developmental sequence of meanings for breast cancer. Methods Fifty women treated for breast cancer, as outpatients by the Breast Surgery Multidisciplinary Team at Hospital S. José, Lisbon, Portugal, were randomly selected and interviewed using a semi‐structured method, in order to obtain data on the significance they attached to their illness. Results A typical breast cancer representation profile was identified: 74% of women know their diagnosis, 70% conceive its causes as external factors, 50% refer to emotional and functional changes as main consequences, 62% are expectant towards the future and 36% considered themselves cured. It was possible to classify women's illness meanings into different developmental levels: the majority of women acceded only to lower (level 2 = 36%) and intermediate levels (level 3 = 50%). A developmental sequence of meanings for breast cancer is presented. Conclusions The identification of women's illness meanings enhances understanding of the emotional reactions and coping processes they use in this stressful situation. Also, it enables the clinician to match clinical methodologies with the patient's developmental level. Cognitive and developmental approaches offer a useful framework for making decisions about prevention and clinical procedures with breast cancer women, which may benefit clinical outcomes. Copyright © 2013 John Wiley & Sons, Ltd.