IntroductionLymphedema in the upper limb as a complication of breast cancer may lead to shoulder pain and dysfunctions. Objective: To compare the scapular positioning, the shoulder range of motion, and muscle strength among women undergoing treatment for breast cancer with and without lymphedema and a control group. MethodsThis cross-sectional study evaluated women undergoing treatment for breast cancer (N = 25) and without lymphedema (N = 25), and a control group (N = 25). Static scapular positions and shoulder range of motion were measured by using an inclinometer. The shoulder and periscapular muscle strength were measured by using a hand-held dynamometer and the Disabilities of the Arm, Shoulder, and Hand Questionnaire was applied. Linear regression of the mixed effects model was used to compare the groups. ResultsBoth groups of mastectomized women had reduced shoulder range of motion, scapular upward rotation, and muscle strength for shoulder and periscapular muscles compared to the control group. Also, women undergoing treatment for breast cancer with lymphedema had reduced shoulder range of motion, scapular upward rotation, increased anterior tilt, reduced muscle strength of the upper trapezius, and greater upper limb disability compared to women without lymphedema. ConclusionWomen undergoing treatment for breast cancer with lymphedema had even greater shoulder and scapulothoracic impairments when compared to the control group and women without lymphedema.