Thymoma is an unusual tumour, but it is the most common malignancy in the anterior mediastinum. This tumour is unique in its frequent association with paraneoplastic syndrome and its potential for indolent growth. The distinction between thymomas and other tumours which arise in the anterior or superior mediastinum is important, and the optimal therapy for these malignancies is quite different. Indeed, even in advanced disease, systemic therapy may not only prolong the disease-free survival, but may also be curative in various malignancies. The therapy for patients with thymoma has been evolving over the past few years.