Malignant diseases are the second most common cause of death in developed countries. Thanks to the advancement of medicine, patient survival has increased over the years and subsequently the need to improve the long-term care of these patients has emerged. As a result, a new area of medicine, named oncofertility, has started to develop. It enables the preservation of fertility in patients with malignant diseases. Chemotherapy and/or radiotherapy lead to decreased ovarian reserve in women and reduced quality of semen in men. There are several ways to preserve fertility in women. Currently used are cryopreservation of embryos and oocytes, cryopreservation of ovarian tissue, application of gonadotrophin-releasing hormone agonists and ovarian transposition. When choosing fertility methods, it is very important to have an individual approach. The chosen method depends on the age of the woman, therapy protocol and time remaining until the start of therapy and the existence of a partner at the time of the fertility preservation process. Cryopreservation of embryos and oocytes are standard methods and have a common step of ovarian stimulation. Various stimulation protocols have been developed to increase the safety of their implementation. The cryopreservation of ovarian tissue is an experimental method that is the only option to preserve fertility in girls before puberty. Continuous administration of gonadotrophin-releasing hormone agonists is recommended in premenopausal women with breast cancer. Ovarian transposition is used to protect fertility when using radiotherapy. The standard method of preserving fertility in boys after puberty and in adult men is cryopreservation of semen. The use of hormone therapy or gonadotropin-releasing hormone agonists is not an effective method. Testicular tissue cryopreservation may be recommended to prepubescent boys, but it is important to note that this is still an experimental method.