In contemporary medical ethics and clinical practice the autonomy of patients and their right to accept or refuse an offered treatment is acknowledged and respected. Prerequisite for the right of a patient to consent to any medical act is the capacity to make valid decisions regarding his/ her treatment. The objective of our study was to assess -for the first time in our country- treatment decision-making capacity of hospitalized patients with schizophrenia; to explore any possible association with demographic and clinical variables; and to compare treatment decision-making capacity of patients with schizophrenia with medical patients' capacity. The sample of patients comprised of 21 patients with schizophrenia who were hospitalized in the psychiatric ward of the General Hospital of Arta, north-west Greece. Those patients' capacity was compared with treatment decision-making capacity of 78 patients hospitalized in the internal medicine ward of the same hospital. All patients' capacity was assessed within 72 hours of admission with the use of the Greek version of the MacArthur Competence Assessment Tool for Treatment (MacCAT-T), a valid and reliable tool for capacity assessment. The performance of patients with schizophrenia on the MacCAT-T was significantly worse than medical patients' performance, suggesting that patients with schizophrenia, as a group had poorer decision-making capacity compared to medical patients. Both negative symptomatology (anergia) and positive symptoms (hostility and suspiciousness), as measured with the use of the Brief Psychiatric Rating Scale (BPRS) were associated with poor performance on the MacCAT-T. Although medical patients as a group scored better in the MacCAT-T, there were several cases that lacked decision-making capacity. In conclusion, patients with schizophrenia had higher incapacity rates than medical patients during the first days of hospitalization. Lack of treatment decision-making capacity is not necessarily the rule for patients with schizophrenia, and capacity is not present in all medical patients. The ability of patients to consent to treatment should be re-assessed during hospitalization, and when restored, informed consent should be obtained by clinicians.