Lymphedema and impairment of function are well-established sequelae to breast cancer treatment and affect an increasing number of women due to continually improved survival. The aim of the present nationwide questionnaire study was to examine the impact of breast cancer treatment on perceived swelling/sensation of heaviness (lymphedema) and on function, reporting prevalence in 12 subgroups of modern treatment and offering estimates for treatment-related associated factors. 3253 Women (87%) returned the study questionnaire. Depending on treatment group prevalence of perceived swelling/heaviness varied from 13 to 65%. Associated factors were young age, axillary lymph node dissection (ALND) and radiotherapy but not type of breast surgery or use of chemotherapy. Depending on treatment group 11-44% had to give up activities. Giving up activities was associated with pain and swelling/heaviness, younger age, ALND, chemotherapy, time elapsed since surgery, and surgery on the dominant side. Radiotherapy and type of breast surgery were of no importance.