Objective: Hydronephrosis developing following ureteroscopy (URS) is an important issue associated with the longtermpostoperative renal functions. Studies investigating the role of postoperative imaging revealed conflicting results.In this study, we aimed to determine the incidence and predictors of hydronephrosis following semirigid URS.Material and methods: We evaluated the results of 455 patients who underwent URS and postoperative imagingwith non-contrast computed tomography (CT). Primary endpoints of the study were to determine the frequency ofdevelopment of hydronephrosis and factors associated with the development of hydronephrosis. Logistic regressionanalysis was used to define factors effecting on the development of hydronephrosis.Results: Postoperative non-contrast CT revealed hydronephrosis in 81 (17.8%) patients. Stone- free status wasachieved in 415 (91.2%) patients. Univariate analysis revealed history of ipsilateral URS (p=0.001), duration of operation(p=0.022), presence of multiple stones (p=0.001), and occurrence of a renal colic episode postoperatively(p=0.013) as the parameters associated with increased risk of postoperative hydronephrosis. In the multivariateanalysis, history of ipsilateral URS (OR: 2.724, p=0.017) and presence of multiple stones (OR: 2.116, p=0.032) werefound to be the independent prognostic markers of developing postoperative hydronephrosis.Conclusion: Ipsilateral hydronephrosis following URS develops in a significant number of patients. In patients withhistory of ipsilateral hydronephrosis and multiple stones, risk of development of postoperative hydronephrosis ishigher, therefore physicians should be keep these parameters in mind in the decision making process of selectiveimaging postoperatively.