The study aimed to assess psychiatric morbidity in medically ill patients and to examine the use of GMHAT/PC Spanish version in a general health setting. We recruited patients who were hospitalized at the services of Internal Medicine, Surgery and G/O during a period of 1 month for each service. The diagnosis of a medical illness was supported by specialists in each service. A trained GP conducted a psychiatric assessment of all the participants using GMHAT/PC. The interview was carried out at patients' bedside. Of 455 medically ill patients, 4.8% had a mental illness identified by GMHAT/PC interview. Anxiety, depression and organic disorders were the most frequently identified mental disorders in internal medicine and surgery. Cancer had a significantly higher prevalence of comorbid mental illness. In this study the proportion of medically ill with mental disorders was less compared to other studies. The GMHAT/PC is more close to identifying clinical cases of mental illness and also patients who need help. The GMHAT is more a diagnostic instrument than a screening instrument. Physicians and practitioners can be trained to identify mental illness using computer-assisted tools such as GMHAT/PC. A holistic approach of providing care to such patients may improve their overall outcome and quality of life.