Background: Herlyn-Werner-Wunderlich Syndrome is a rare malformation syndrome characterized by uterus didelphys with obstructed hemivagina and ipsilateral renal agenesis. Symptoms appear most often after menarche and are secondary to hematocolpos. We compare clinical symptoms, diagnosis and treatment of two patients, a 13-year-old and a 17-year-old. Case report: Despite the non-uniform clinical symptoms, it should be noted that in both patients, the 13-year-old and the 17-year-old, hematocolpos, which was probably the cause of lower abdominal pain, was diagnosed with ultrasound. The diagnosis was complemented by laparoscopy, which determined the diagnosis of malformation of uterus didelphys with obstructed hemivagina. The patients had a history of kidney agenesis, which, after gynecological diagnosis, turned out to be ipsilateral. In the 13-year-old, agenesis was diagnosed by uroscintigraphy, while in the 17-year-old it was diagnosed by urography. Incision and drainage of the residual vagina was performed in the course of therapeutic management. In both cases, the clinical situation required a repeated widening of the orifice. Conclusions: Lower abdominal pain accompanying hematocolpos suggested Herlyn-Werner-Wunderlich Syndrome (HWWS) as the cause of symptoms. 3D transvaginal ultrasound enabled the determination of a congenital uterine defect with high probability, although inconclusive cases required confirmation by laparoscopy. Incision of the blocked vagina and drainage of hematocolpos were the key components of treatment. The treatment of HWWS is a multi-step process.