Xanthogranulomatous pyelonephritis is a chronic inflammatory renal infection usually seen in middle aged women but extremely rare in children. In this study 18 patients (6 of them were children) with xanthogranulomatous pyelonephritis are reported. Preoperative picture was similar to calculous pyonephrosis, and malnutrition and maldevelopment were seen in these children. Although ultrasonography and computed tomography (CT) suggested per- inephritic and retroperitoneal invasion (like psoas abscess), the final diagnosis was established by histologic examination. Following surgical therapy (15 nephrectomy and 3 nephroureterectomy) patients showed excellent improvement.