A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was 'Does surgical debulking for advanced stages of thymoma improve survival?' Altogether, only 17 papers were found using the reported search, of which only 10 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated; these studies have mainly reported the survival and recurrence rates after total vs subtotal resection of thymic tumours in patients receiving or not receiving adjuvant chemoradiotherapy. These studies confirmed that complete resection is the best prognostic factor in thymomas. With regard to subtotal tumour resection/debulking, we did not find any randomized controlled trials. The evidence on this topic is scarce and these 10 reported were retrospective reviews of the operative, histology and survival data of patients with thymoma who had subtotal vs partial resection for advanced stages of thymoma. Although debulking surgery for thymoma had positively affected survival, in six studies, the difference failed to reach statistical significance. Three of the studies, on the other hand, showed a higher survival rate in thymomas in which maximum debulking was performed and the treatment was followed by high-dose irradiation. None of these studies showed any benefit in debulking surgery for thymic carcinoma. Besides histology and tumour cell-type, other factors influencing survival included the tumour stage and the presence of symptoms such as myasthenia gravis as a warning sign at an early stage. Current evidence in the literature on the survival after debulking surgery for thymoma is contradictory, and most of the studies do not show any survival benefit after debulking for thymoma. However, debulking surgery minimizes the tumour size and area for irradiation postoperatively, hence it can result in less damage to the adjacent tissue during radiotherapy and may be considered for patients in advanced stages of thymoma in whom extensive radiotherapy will be required. In these cases, however, the risks of surgery followed by radiotherapy or radiotherapy alone should carefully be assessed prior to the initiation of treatment.