The purpose of this paper is to describe a case of juvenile cystic adenomyoma in a 17 year-old female patient with severe dysmenorrhoea unresponsive to non-steroidal anti-inflammatory drugs. The patient presents progressively worsening dysmenorrhoea that started 2 years after menarche and a cystic uterine lesion in MRI. The cyclic nature of symptoms, the similarity of the lesion and endometrium in MRI signal intensity and response to hormone suppression are consistent with juvenile cystic adenomyoma. The treatment depends on the age of the patient, severity of her symptoms and size and localisation of the cyst. This is a rare condition in young nulliparous women with a challenging differential diagnosis. This case highlights the relevance of MRI in the patient's study, featuring important characteristics of the lesion that disclosed the final diagnosis.