Traditionally, the test of the lung mechanical function (LMF) has been carried out with the patient's active collaboration. In the fifties, it was possible to have mechanical means available to determine the lung mechanical function, causing a great development of its knowledge. Lately, the use of isotopes in medicine, because of their availability in the clinic, took an active part in the development of this new medical specialty. Nowadays, due to the development of the technology, it is possible to obtain the LMF in a quick way, avoiding the patient's collaboration, just from one frontal view chest radiograph. The system uses variables which are different from the traditional ones as a result of two factors: (1) its theoretical basis (General Systems Theory), and (2) the technology used (CCD camera, PC/AT-386, image board, two monitors, magneto-optical disk, laser printer and video printer). The diagnosis system has been tested and validated in the Hospital Central de Asturias, Oviedo, Spain.