Background: The Item Response Theory (IRT) has advantages for measuring Health Related Quality of Life (HRQOL) as opposed to the Classical Tests Theory (CTT). Objectives: To present the results of the application of a polytomous model based on IRT, specifically, the Rating Scale Model (RSM), to measure HRQOL with the EORTC QLQ-C30. Methods: 103 terminal cancer patients cared for by the home services of the Servicio Andaluz de Salud (Andalusian Health Service) (Andalusia, Spain) participated. These patients responded to the adapted Spanish version of the EORTC QLQ-C30. The application was carried out individually in the patients' homes. Results: The results show that there is an adequate global fit between the data and the IRT model applied. The analysis of the items shows that for 31 of the 33 items there is a good fit. The items which measure the general perception of health and the perception of quality of life present a lack of fit. The study of the response categories of the items (by means of Category Probability Curves) indicates that all the alternatives work extremely well. Conclusions: The EORTC QLQ-C30 presents good metric qualities, under the RSM, ratifying the feasibility to measure HRQOL already shown in other studies carried out with CTT.