Quality is always an important issue for health care institutions to address. In academic field, most of research discussed about the quality performance drivers based on one or two factors. However, in practical societies, there are numbers of factors influencing on the quality of health service, such as physician factors, treatment process factors, and patient factors. This paper tries to examine how the three factors mentioned above to influence the quality of health care. We select two kinds of health cares---cataract surgery and intense care unit as analyzing samples. Cataract surgery is quite popular surgery among elder people. The clinical process of cataract surgery is already standardized and is included in the case payment categories in Taiwan health care system. However, the processes of intensive care are so complex, and the severity of the patients in intensive care is various. We can get more thorough understanding the quality performance drivers of health care by comparing the drivers of one simple and one complicated diseases.