Objective: To compare the influence of breast-conserving surgery (BCS) and modified radical mastectomy (MRM) on the psychological state of breast cancer patients. Methods: Patients receiving MRM or BCS, and fulfilling the study criteria, were recruited. Patients were required to complete a self-reporting inventory (SCL-90) on admission and 6 months after surgery and a self-rating depression scale (SDS) when discharged from hospital and 6 months after surgery. Results: A total of 70 patients received MRM and 50 BCS. Compared with the national standard, patients suffered to some extent psychological problems on admission, at discharge from hospital and at 6 months after surgery. Patients received BCS had a higher score of SDS compared with those with MRM when discharged from hospital. However, 6 months after surgery, SDS score increased in MRM and decreased in the BCS group, so the difference was significant. Conclusion: The short-term psychological state of patients receiving BCS is worse than that with MRM but superior to MRM 6 months postoperatively. BCS imposed less influence on long term psychological state of breast cancer patients compared with MRM.