In China, not only patients and physicians are involved in medical decision-making (MDM) but also the patients' family members. The objective is to investigate the willingness and actual situation of cancer patients and their family members participating in the MDM process. In this cross-sectional study, questionnaires were administered to 247 pairs of cancer inpatients and their relatives. Information regarding participants' willingness and actual experience during the decision-making process was documented. Eligible participants were cancer inpatients or their relatives, 18 years of age or older, and informed of the cancer diagnosis. All the patients should have received chemotherapy. The effective response rate was 72.9% (180/247). Over half of the patients (53.3%) and family members (57.8%) were willing to be part of the MDM process. In contrast, only 35.0% of patients and 46.1% of family members actually experienced this process (p = 0.001 and p = 0.011, respectively). Fewer family members (42.2%) than patients (53.3%) believed that patients should be involved in the MDM process (p < 0.001). Patients who were the head of their family (odds ratio 2.577, 95% CI 1.198-5.556, p = 0.015) experienced more involvement in MDM. Although more than half of Chinese cancer patients and family members wanted to be part of MDM, the actual participation was below their expectation. Majority of family members do not want the patients to be involved in the process of MDM. Copyright © 2015 John Wiley & Sons, Ltd.