This study aims at assessing psychiatric morbidity in medically ill patients, as well as examining the employability of the Global Mental Health Assessment Tool - Primary Care (GMHAT-PC) Spanish version in a general health setting. The participants in this study are recruited patients who were hospitalized at the services of Internal Medicine, Surgery and Gynaecology and Obstetrics for a period of one month. The diagnosis of a medical illness was supported by specialists in each service. Also, a trained general practitioner conducted a psychiatric assessment of all the participants making use of GMHAT-PC. It is worth noting that every single interview was carried out at the patient’s bedside. With regards to specific numbers, out of 455 medically ill patients, 4.8% had a mental illness identified by dint of the GMHAT-PC interview. Anxiety, depression and mental organic disorders were the most frequently identified mental disorders in internal medicine and surgery. On the other hand, cancer had a significantly higher prevalence of comorbid mental illness. In this study, the proportion of medically ill subjects with mental disorders was markedly lower in contrast with other studies. It was determined that GMHAT-PC is more likely to identify not only clinical cases of mental illness, but also patients who need help. Thus, it can be argued that GMHAT-PC is more of a diagnostic instrument than a screening instrument. It goes without saying that physicians and practitioners can be trained to identify mental illnesses 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.