A diverse group of congenital, cystic, and neoplastic conditions can present as a renal mass in children. Hydronephrosis and multicystic dysplastic kidney are the most common benign causes in neonates, whereas Wilms’ tumor represents the predominant malignant neoplasm in childhood. Other entities such as clear cell sarcoma, rhabdoid tumor, congenital mesoblastic nephroma, and renal cell carcinoma occur less frequently. Ultrasonography serves as the primary imaging modality, while CT and MRI provide essential information for characterization, staging, and follow-up. Recognition of age-specific patterns and imaging features is crucial for accurate diagnosis, appropriate management.