Primary mediastino pulmonary tuberculosis in infancy is increasing in France. Bacteriological diagnosis is difficult. The aim of the study is to assess the value of chest radiograph and CTscan for diagnosis of tuberculosis. We studied 15 infants, 3 month old to 18 month old, between November 1990 and June 1992. On plain film, lymphadenopathies were present in 13 cases and parenchymal disease in 10 cases, parenchymal nodular densities in 6 cases and pleural effusion in one case, displacement of the trachea in 6 cases. We found CTscan to be useful in delineating the lymphadenopathies and parenchymal changes. In 2 cases lymphadenopathies and in 2 cases alveolar condensation were discovered on CTscan as plain film was normal. In all cases lymphadenopathies were present in CTscan, often in right side and in all cases, lymphadenopathies were hypodense with peripheral enhancement. In conclusion, the association of right paratracheal nodes with displacement of trachea and alveolar consolidation is common in tuberculosis in infants. These findings when seen on chest radiographs must lead to perform a CTscan and suggest the diagnosis.