It is anticipated that an inherited/familial forms of pheochromocytomas cause approximately 20% of all pheochromocytomas. Therefore, the classic "rule of 10" axioma used to remember the key features of disorder is invalid. Various mutations in several genes have been identified, which underly syndromes with paragangliomas and/or pheochromocytomas. The more candidate genes, the less numbers of patients with apparently sporadic forms of the disorder. This review has summarized the current knowledge of the genetic background of tumors orginating from adrenomedullar and extra-adrenal chromaffin tissue.