Cryopreserving and transplanting ovarian tissue is a safe way to preserve fertility in cancer patients at risk of infertility after treatment. In Hungary, the first three cases of successful ovarian tissue autotransplantation in patients with malignancies have been reported. This method has led to nearly a hundred live births worldwide and is as effective as other fertility treatments. Thirteen patients with stage I-III cancer were included in the study, and after successful treatment, ovarian tissue was thawed and transplanted back into three patients. The procedure was done laparoscopically or with a small incision, and all patients recovered well. This technology is a viable option for preserving fertility before cancer treatment, after careful evaluation of each patient's situation.