Background: Lymphangiomas occurs in children quite frequently. They are most commonly localized in the head, neck, axilla, chest, abdomen, and retroperitoneum. Lymphangiomas of the scrotum are very rare and are usually clinically silent, so they are a challenge for radiologists performing US examination in children. They are obliged to differentiate the following lesions: torsion of the testicle, scrotal hernia, hydrocoele, and epididymal cyst, in addition to the masses of primary extratesticular localization such as hemagioma, congenital vascular malformations, fibromas, and malignant tumors. Additional difficulties appear in boys who present acute scrotum syndrome. Case Report: The paper reports the diagnostics and treatment of a huge multicystic lymphangioma situated in the scrotum and retroperitoneum of a 12-year-old boy who had fallen from a bicycle and presented acute scrotum. The lesion of the scrotum was surgically excised. Retroperitoneal lymphangioma was detected during this operation. Subsequent diagnostics was based on ultrasonography, computerized tomography, and magnetic resonance imaging of the abdominal cavity. The lymphangioma of the retroperitoneum was resected. The patient shows no evidence of recurrence after 7 years. Conclusions: Cystic lymphangiomas are rare but benign intrascrotal, extratesticular, painless masses in children. They are sonographically multicystic or multiloculated abnormalities and may show infiltrative extension to the perineum, retroperitoneum, or abdomen. Recognition of this entity and its extent is important for correct clinical management and may be for planning treatment.