A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed whether [surgery] has a role in [treatment of T4N0 and T4N1 lung cancer]. Altogether more than 151 papers were found using the reported search, of which 15 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. We conclude that upfront surgery for locally invasive T4 tumours without mediastinal lymph node involvement (T4N0 and T4N1 non-small cell lung cancer) is of benefit in terms of survival rates in carefully selected patients. Overall five-year survival rates following resection of T4N0-N2 tumours vary from 19.1% to 57% (from six studies), within which, involvement of certain structures were found to greatly affect prognosis. Pulmonary artery invasion has a good prognosis (five-year survival; 52.8%) relative to other mediastinal structures [five-year survival: left atrium; N0; 28.94%, N1; 27.92%, N2; 17.95% (three-year survival), aorta; N0; 100%, N1; 37.1%, N2; 0%, superior vena cava (SVC); 11%, -29.4% (from four studies), carina; 28-42.5% (two studies), veterbral bodies; 16%, oesophagus; 12%, pleural dissemination; 0%]. When considering isolated invasion of the pulmonary great vessels there are mixed outcomes, one study reporting reduced mortality (reduced risk -0.483, P=0.004) in contrast to another that found five-year survival of 35.7% with great vessel invasion vs. 58.3% for invasion of all other structures excluding the pulmonary great vessels. The prognostic variables found to be of greatest determinacy were; first, the completeness of resection, wherein five-year survival rates ranged from 37.5 to 46.2% (from three studies) with complete tumour removal, and 15.9-22.4% (from three studies) with incomplete resection, and second, nodal status of the patients, N0/N1 having five-year survival of 43-74% and N2 of 15.1-17.5% (P=0.022 and P=0.007, for two studies). Multiple intralobar lesions represent either multilobar metastasis or NSCLC with multifocal origin and have been found to behave differently to invasive T4 tumours. Reported five-year survival in NSCLC with satellite nodules is 48.2-57% compared with 18-30% from T4 invasive tumours (three studies), respectively (P=0.011) corroborating the change in TNM ipsilobar multifocal T4 disease to be recoded as T3.