The effects of ureteral stent diameters on ureteral stent-related symptoms were evaluated by using Turkish-validated Ureteral Stent Related Symptoms Questionnaire (USSQ). Datas on 126 patients underwent uncomplicated flexible ureterorenoscopy and 62 patients underwent uncomplicated semirigid ureteroscopy surgery without stent insertion (group 3) were collected. Patients were randomized preoperatively in a double-blind fashion to 4.8 French (group 1) and 6 French (group 2) ureteral JJ stents groups. The first follow-up visit was done at one week after surgery for all groups. Stents were removed on the third postoperative week for stented groups. The second follow-up visit was done at one week after stent removal for group 1 and group 2, and four week after surgery for group 3. Preoperative characteristics, operation time and hospitalization times were similar in both groups. Total USSQ scores were 91.9, 103.0, 44.2 at first visit and 54.3, 58.7, 28.5 at second visit in group 1, group 2, and group 3, respectively. At both first and second visits, the group 2 had significantly higher USSQ scores than the group 1 (p = 0.01 and p < 0.001, respectively). Group 1 and 2 had higher scores than group 3 at both visits. Ureteral stents are associated with poor effects on patients’ comfort and high USSQ scores. Using 4.8 Fr JJ stents improves stent-related symptoms and decreases the USSQ score more than 6 Fr JJ stents. Therefore, if ureteral stent is to be used after URS, we recommend using 4.8 Fr stent.