The increased radiation level after Chernobyl catastrophe changed the structure of morbidity in Belarus and also influenced on pathogenesis and clinical features of internal diseases. We compared the pecularities of pulmonary tuberculosis and chronic lung diseases in two groups: in patients having been exposured to irradiation (Chernobyl catastrophe liquidators and inhabitants in radionuclide polluted territories) and in non-exposured patients (inhabitants of Minsk and Minsk district).  For the first group in patients with pulmonary tuberculosis there was rise in disease severity with tendency to chronisation, more frequent complications such as bronchial tuberculosis and non-specific bronchitis, antituberculosis drug resistence, prolonged hospital stay and in some cases diseases progressed resulting in patients deaths. In patients with chronic pulmonary diseases after radiation exposure the exacerbations were 1.5 times greater comparing with second group. We considered that one of reasons for pathomorphosis of lung diseases may be functional alteration of monocytes and alveolar macrophages, in particular changes in production tumor necrosis factor (TNF). In first group of patients with pulmonary tuberculosis the spon taneous syntesis of  TNF was activated, but induced syntesis was reduced; there were also increased level of monoc ins and reduced level in bronchoalveolar lavage fluid (BALF). In patients with chronic lung diseases the a tivation of spontaneous synthesis of TNF and reduction of induced synthesis of  TNF were more significant. In patients with chronic lung diseases living in radionuclide polluted territories the decreased level of TNF in BALF was revealed. The disorders of TNF synthesis and it’s contents in biological fluids correlated with clinical course of diseases.