Objective: Our objective in this study was to present the data for patients followed-up and underwent surgery due to complex renal cyst using Bosniak classification system. Method: Data of all patients followed-up or underwent surgery via open / minimal invasive methods due to complex renal cyst in our clinic between 2016 and 2019 were retrospectively evaluated. Bosniak category IIF and higher lesions were included in the study. Results: A total of 83 patients were included in the study. The mean age of the patients was 52 ±10.1 years and 40 (48.2%) were male and 43 (51.8%) were female. 53 (63.9%) patients had Bosniak IIF, 18 (21.7%) patients had Bosniak III and 12 (14.5%) patients had Bosniak IV lesions. Mean lesion size was 54±27.4 mm. Surgery was performed in a total of 41 (49.4%) patients. Based on final pathology result, while benign pathologies were detected in 13 (31.7%) patients, clear cell renal cell carcinoma was detected in 22 (53.7%) patients and papillary renal cell carcinoma in 6 (14.6%) patients. Malignity rates were detected as 18.9%, 44.4% and 83.3% in Bosniak IIF, III and IV lesions respectively. While the mean lesion size of patients who had benign pathology were 64.6±18.4 mm, mean lesion size of patients with malign pathology were 58.3±29.7 mm (p =.41). Conclusion: Progression is an important malignity finding in Bosniak IIF lesions. An important amount of especially Bosniak III lesions is overtreated. Thus, active surveillance is a treatment which should be considered in these patients. More comprehensive prospective randomized studies are needed.