Medical second opinion is a decision-support tool for ratification or modification of a suggested treatment, by another physician. A medical second opinion may have a critical influence on the diagnosis, treatment, and prognosis. The patient can benefit from treatment optimization and avoid unnecessary risks. The physician can benefit from less exposure to legal claims, and healthcare organizations can benefit from increased treatment, quality assurance and costs saving from unnecessary surgery and treatments. Nevertheless, injudicious use of this tool can provoke unnecessary medical costs. In recent years, many patients prefer to seek a second opinion on their disease and available treatments. Private and public insurance companies are trying to control surgery costs by urging and even demanding a second opinion before surgery. Although medical second opinions are common in medical practice, relatively little is known on this subject.