Introduction & Objective: No study examined patients’ lung capacities after standard and single port VATS, Therefore, in this study we decided to compare the results of standard VATS and single-incision Thoracoscopic surgery (SITS) in patients undergoing diagnostic Thoracoscopic. Materials & Methods: In this randomized clinical trial, patients referred for diagnostic Thoracoscopic to Modarres hospital in years 2015 to 2017 were enrolled the study, Then, patients were divided into two groups using the Random allocation software: one group underwent Thoracoscopic with one port and the other group underwent Thoracoscopic was performed by standard methods (3 Ports). Then both groups of patients in respiratory capacity (FEV1, FEV1 / FVC), postoperative pain, complications and length of hospital stay and demographic variables were compared. Results: From 27 patients 14 patients were in the Single port VATS and 13 patients in the Standard 3 port VATS groups. Patients’ satisfaction was higher in SITS group (P = 0.011). Paresthesia of surgical site in patients SITS was significantly lower (P = 0.029).The hospital stay after surgery was lower in the group SITS (0.009). 24 hours post-operative and discharge time pain in SITS group was lower (P