Aim:We aimed to determine the impact of BMI (body mass index) on extracorporeal shock wave lithotripsy (SWL) success.Material and Methods: We retrospectively analyzed the medical records of all patients who underwent SWL for single renal stone smaller than 1.5 cm. Patient demographics, height, weight and stone characteristics were recorded. Stone free (SF) patients and patients with residual stone (RS) were compared according to BMI, mean HU (Hounsfield unit), stone size and number and duration of shock waves.Results:A total of 100 patients with an average age of 48.17 ± 1.58 years and an average stone size of 9.54 ± 1.61 mm were included the study. Overall SWL success was 69 % such 31 patients had RS. SF status achieved in 85%, 57.1%, 58.1% and 78.6% of patients with renal stones in upper, middle, lower calyces and renal pelvis, respectively. Mean BMI and mean stone sizes were found significantly different between SF and RS groups, 25.3 ± 3.5 kg/m2 versus 30 ± 3.4 kg/m2, 8.7 ± 1.3 mm versus 9.7 ± 1.6 mm, respectively (p< 0.001). The best cut-off value, which was found according to Youden’s index, for BMI for a successful SWL was 26.75 kg/m2.Discussion:These preliminary results may lead further studies with large patient numbers to determine a threshold of BMI for to predict SWL success.