Aim: To evaluate resistive index (RI) changes before and after unilateral percutaneous nephrolithotripsy in chronic partially obstructed kidneys due to ureteropelvic junction (UPJ) stones. Methods: Intrarenal RI of obstructed and contralateral normal kidneys of 18 patients were recorded immediately before the operations and at postoperative days 1, 7 and 30. Postoperative RI measurements were compared with baseline values for all patients without grouping and separately for different groups according to the preoperative RI value of the obstructed kidney. Results: Mean age and symptom duration were 27.5 years and 43.8 weeks, respectively. Preoperatively and at all postoperative controls, kidney diameters and renal parenchyma thicknesses were normal in all patients. Mean RI of obstructed kidneys decreased from 0.68 to 0.63 for all patients (P = 0.032), from 0.64 to 0.63 for those with preoperative RI < 0.70 (P = 0.850) and from 0.73 to 0.62 for those with preoperative RI ≥ 0.70 (P = 0.001). In patients with preoperative RI ≥ 0.70 in obstructed kidney, significant RI decreases were recorded at postoperative day 7 and RI differences between obstructed and contralateral kidneys disappeared after then. No difference was present pre‐ and postoperatively between the mean RI of obstructed and contralateral kidneys of the patients with RI < 0.70. Mean RI of contralateral kidneys were normal preoperatively and showed no significant change postoperatively. Conclusions: Preoperative RI levels may indirectly reflect the presence of functionally significant obstruction in chronic obstructed kidneys related to UPJ stones. Patients with RI ≥ 0.70 may have a good indication for a surgical approach. Normalization of high RI occurs rapidly after percutaneous nephrolithotripsy.