Clinical Decision Support Systems help a physician by suggesting a diagnosis based on findings and/or suggesting a treatment. Diagnostic support can be especially useful for rare and complex diseases, though planning support for therapies is an even more interesting application of CDSSs, since it supports evidence-based medicine (EBM) and best practices. Programs that support diagnostic decision making have been shown to improve a physician's diagnostic performance significantly. Medical knowledge and technologies evolve constantly, and new diagnostic and therapeutic means become available and have an impact on what is considered the most efficient way to heal a patient. Based on knowledge that kept up-to-date, a CDSS can offer valuable support to physicians.