Background In clinical practice,the mechanisms underlying chronic post-surgical pain (CPSP) remain insufficientlyunderstood.The primary goals of this study were to determine the incidence of chronic pain after thoracic surgery and to identify possible risk factors associated with the development of chronic post-thoracotomy pain in Chinese patients.The secondary goal was to determine whether the difference between pre-and post-operative white blood cell (WBC) counts could predict the prevalence of CPSP after thoracotomy.The impact of chronic pain on daily life was also investigated.Methods We contacted by phone 607 patients who had undergone thoracotomy at our hospital during the period February 2009 to May 2010.Statistical comparisons were made between patients with or without CPSP.Results Results were ultimately analyzed from 466 qualified patients.The overall incidence of CPSP was 64.5％.Difference between pre-and post-operative WBC counts differed significantly between patients with or without CPSP (P＜0.001) and was considered as an independent risk factor for the development of CPSP following thoracotomy (P＜0.001).Other predictive factors for chronic pain included younger age (＜60 years,P ＜0.001),diabetes mellitus (P=0.023),acute post-operative pain (P=0.005) and the duration of chest tube drainage (P ＜0.001).At the time of interviews,the pain resulted in at least moderate restriction of daily activities in 15％ of the patients,of which only 16 patients had paid a visit to the doctor and only three of them were satisfied with the therapeutic effects.Conclusions Chronic pain is common after thoracotomy.WBC count may be a new independent risk factoring surgical patients during peri-operative period.Besides,age,diabetes mellitus,acute post-operative pain,and duration of chest tube drainage may also play a role in chronic post-surgical pain occurrence.