Moderate-severe pain after surgical procedures is associated with decreased quality of life and increased costs. this study aimed to identify the incidence and predictive factors of moderate-severe postoperative pain within 48 hours following video-assisted thoracoscopic surgery (VATS) in a tertiary hospital. A retrospective cohort analysis was performed using medical records of adult patients who underwent VATS between January 2015 and December 2016. Logistic regression was performed to identify predictive factors for moderate-severe pain (visual analogue scale, VAS ≥ 4) within 24 hours and within 48 hours postoperatively. Of the 1164 participants, the incidence of moderate-severe pain was 12.7% within the first 24 hours and 15.6% within the first 48 hours after surgery. In multivariable analysis, the independent risk factors related to moderate-severe pain within 24 hours after surgery were younger age, increased body mass index, preoperative pain within 1 month and history of smoking. The risk factors for moderate-severe acute pain within 48 hours were almost the same, except that the number of chest tubes were also included. Moderate-severe postoperative pain following VATS is not rare, and presence of several risk factors deserves more aggressive pain management strategies perioperatively. Moderate-severe pain after surgical procedures is associated with prolonged hospital stays, readmissions, patient dissatisfaction, development of chronic pain, decreased quality of life and increased costs 1,2. It is widely accepted that better management of postoperative pain results in better patients' recovery. Video assisted thoracoscopic surgery (VATS), compared to conventional thoracotomy, is notable for less tissue trauma, improved postoperative respiratory function, and increased tolerability for the patients 3. Although potentially less postoperative pain was generally expected as one of the benefits of VATS 4 , many patients still suffer moderate to severe pain postoperatively 2,5-7. There are several reasons contributing to this unsatisfactory situation, one of them being that some patients may have certain risk factors for occurrence of more severe postoperative pain 8. Early identification of patients at risk may help to allow early application of effective treatment strategies to prevent unexpected suffering in these patients. Previously, several studies have focused on the predictors of postoperative pain and demographic, social psychological and clinical factors have been identified contributing to the development of severe postoperative pain 5,6,8,9. However, most of them are cohorts with mixed surgical procedures while VATS is not included. Moreover, various subtypes of VATS (uniportal, multiportal and robotic) exist currently, and the lack of guideline results in variation of analgesia regimens and effectiveness of analgesia in different medical centers 10. To date, the predictive factors of moderate-severe postoperative pain following VATS were not reported, which is important for individual-specific pa...