This study aimed to evaluate whether the incidental finding of the mammary lesions was influenced by the patient’s arm position and respiration style during liver magnetic resonance imaging (MRI). If the mammary lesion was detected earlier, treatment could be performed earlier. Therefore, the finding of mammary lesion during liver studies was useful information. The incidental detection of mammary lesions was influenced by the patient’s arm position and breathing style. Unexpected mammary lesions could be detected when the arms were positioned at the sides of the body and the exhalation style was used during liver MRI.