An inflammatory tumour of the prostate is very rare in young boys without genital anomalies. We report a 4.5-year-old boy presenting with pollakisuria, dysuria, secondary urinary incontinence and decreased urine stream. Ultrasonography, magnetic resonance imaging and transrectal tumour biopsy justified the diagnosis of an inflammatory tumour of the prostate with a size of 5x3x5cm. Under antibiotic therapy the clinical symptoms disappeared within 6weeks. Three months later ultrasonography revealed a normal prostate with a residual midline cyst of 3x4mm. Follow-up examinations for 2years did not show any evidence of relapse. We believe that the inflammatory tumour can be explained by the embryologic development of the prostate and the persistence of an intraprostatic cyst.