The main goal of this study was to investigate possible residua of thymic tissue in 100 adult cadavers with no thoracic pathology known before, by dissection of standard locations of thymic tissue in perithyroid, periaortic, peritracheal and retrotracheal spaces, as well as areas located next to the course of phrenic, vagus and left recurrent laryngeal nerves. Thus obtained tissue samples were studied by two pathologists independently. The remnants of the thymic tissue were found in 61 out of 100 specimens studied. It means that residua of ectopic thymic tissue is common, which may have a huge impact on the results of treatment of many diseases i.e. myasthenia gravis in course of thymoma.