Following an overall view of the emotional situation of primary breast cancer patients and of studies exploring shared decision making in this setting we present the results of qualitative analyses about breaking bad news situations and interviews with this group of patients and describe both methods for implementing shared decision making in the treatment of primary breast cancer and an evaluation study. The main result was that most patients showed a lack of information about breast cancer and its therapy, which led to uncertainty. Another source of uncertainty was the lack of preoperative punch biopsy. Due to the so-called "diagnostic shock" patients felt under pressure to make a quick decision over their treatment. This perceived pressure can be effectively countered by a shared decision making approach. To investigate the options in breast cancer therapy, decision aids for diagnostic and therapeutic options have been developed focusing on the following treatment modalities: 1. breast conserving therapy and radiation versus radical mastectomy 2. chemotherapy plus endocrine therapy versus endocrine therapy alone 3. preoperative versus postoperative chemotherapy. The decision instruments in question were tested in N = 35 breast cancer patients and N = 36 nurses as a control group. The results of a questionnaire survey among both these groups revealed a very positive appraisal of the decision aids. Implementation in daily routine was favoured.