Over the past decades, major advances in diagnosis and treatment have markedly improved the rates of cure for many young adults and children cancers. As a result, the field of fertility preservation (FP) has developed to overcome the adverse effects of cancer treatments on gonadal function. The strategy of FP will depend on patient's age, the puberty status, and the time frame before the initiation of gonadotoxic treatments. Embryo or oocyte cryopreservation after controlled ovarian hyperstimulation is currently the most established technique of FP, but ovarian tissue freezing may also be offered despite it is still considered experimental. More recently, in vitro maturation (IVM) of oocyte has been proposed in the strategy of FP since it does not require ovarian stimulation and can be performed at any time of the menstrual cycle. Therefore, IVM represents an attractive approach for urgent FP or/and in patients suffering from estrogen-sensitive cancers. In addition, GnRH agonists administration during chemotherapy has also been considered as a technique of FP, with controversial results.