Background: Percutaneous nephrolithotomy (PCNL) is the gold standard treatment for renal stones ≥2cm, and it could be an option in some patients with renal stones less than centimeters. Objectives: To evaluate the safety and practicability of the 90° puncture technique in prone percutaneous nephrolithotomy in pediatric age group. Patients and Methods: This prospective cohort study was conducted at urology department Zagazig University Hospital on 18 cases less than 18 years old with renal stones >2cm. imaging study, non-contrast spiral computer tomography (NCSCT), was performed on all patients. Postoperative assessment is measured by recording the rate of success of the modified biplanar 90° puncture technique, the length of hospital stay and any postoperative complications. Results: Kidney stones are found in the renal pelvis in 38.9%, lower calyx in 27.8%, middle calyx in 22.2% and the upper calyx in 11.1% of children. The kidney stone ranged in size from 21 to 31mm, with a mean size of 26.1±2.9 mm. Of the mini-PCNLs, 25 were left-sided (71.4%) and 10 were right-sided (28.6%). The stone density ranged from 923 to 1340 with a mean of around (1056±126). 6 patients (33.3%) experienced problems; 2 patients (11.1%) experienced bleeding; 2 patients experienced fever and 2 patients had infection. When managing kidney stones between two and three centimeters in size. Conclusion: In the pediatric age range, the modified biplanar 90° puncture approach showed to be a safe and effective method with fewer problems for the therapy of kidney stones measuring 2-3cm.