There are frequently respiratory complications with cancer particularly in primary lung carcinoma. Among these are bronchopulmonary infections with or without endobronchial obstruction, carcinomatous lymphangitis, thromboembolic disease and haemorrhagic disease as well. Radiotherapy and chemotherapy may induce various respiratory complications which diagnosis can be of varying shades of difficulty. The classical post radiation pneumonitis occurring exclusively in the field of radiation hardly poses any problem unless it could be masking a recurrence. Certain clinical manifestations address very difficult problems of differential diagnosis by their lack of specificity and by their often unforeseeable character (except for bleomycin fibrosis which is perfectly dose dependent). Moreover patients often have multiple treatments and the identification of the single responsible agent becomes very difficult. We will not discuss here the infectious or secondary haemorrhagic complications of radiotherapy or chemotherapy but rather the anaphylactic manifestations, diffuse interstitial pneumonia with lymphocytic alveolitis or fibrosis, eosinophilic pneumonia, non-cardiogenic pulmonary oedema, bronchiolitis obliterans with organising pneumonia and the rare pulmonary vascular disorders such as pulmonary veno-occlusive disease.