Abstract Purpose: Ovarian lesions are rarely encountered in children. Even so, one might find the whole spectrum of different pathologies in this age group, from benign non-neoplastic cysts that do not require treatment to highly malignant neoplasms that need radical surgical intervention. This thesis looks at the epidemiology of ovarian lesions among children and adolescents, what surgical treatment is currently recommended, and evaluates how this corresponds with the treatment given for these conditions at OUS Rikshospitalet. Methods: An unsystematic search in PubMed with the words ovarian lesions , ovarian tumours , ovarian cysts , ovarian cancer , children , surgery and treatment in different combinations was conducted to identify relevant literature on the topic. A retrospective review of children treated for ovarian lesions at OUS Rikshospitalet during the period from July 2006 until November 2012 was then performed. Results: A total of 25 patients treated at OUS Rikshospitalet were evaluated as part of this thesis. 18 patients had benign disease, either cysts or benign neoplasms, while 7 patients had malignant tumours. Cystectomy was performed on 2 patients with cysts. The rest of the patients with benign conditions were operated on with oophorectomy or salpingo-oophorectomy. Malignant tumours were treated with either oophorectomy or salpingo-oophorectomy followed by appropriate adjuvant therapy. Conclusion: Most ovarian lesions during childhood are benign with cysts being most common. Both benign and malignant neoplasms are predominantly of germ cell origin. Ovary sparing surgery with cystectomy and tumour enucleation is recommended for benign disease, while for malignancies the approach generally should be unilateral salpingo-oophorectomy. When it comes to treating benign disease with ovary sparing techniques there is a potential for improvement at OUS Rikshospitalet.