In immunocompromised patients interventional modalities have diagnostic and/or therapeutic purposes--in both cases they are justified on the basis of the frequently aspecific clinical and instrumental findings and because of the clinical need to carry out the most specific treatment as soon as possible. The authors stress the particular weakness of immunocompromised patients to invasive approaches and discuss the indications, contraindications and precautions which must be taken when performing interventional radiologic modalities. Diagnostic imaging uses radioscopy, US and CT for guidance, each of them allowing a rapid percutaneous confirmation of lesion nature, the assessment of infection in a collection, of a neoplastic lesion type, or of the microbiology of an infectious lesion. Interventional modalities are frequently indicated in chest diseases--e.g., for punctures and percutaneous drainage of empyematous pleural collections or of pulmonary abscesses, percutaneous needle biopsies of lung lesions, or endoscopic dilatation of tracheobronchial stenoses. The percutaneous drainage of lung abscesses in immunocompromised patients makes recovery easier. The diagnostic accuracy of the results of needle biopsy is lower in lung infections than in neoplastic lesions. Indications to abdominal interventional procedures are less frequent--i.e., percutaneous drainage of rare abscesses, percutaneous needle biopsy of nodal mesenteric or lumboaortic masses. Some clinical conditions are diagnosed only with invasive radiologic procedures--e.g., ERCP diagnoses sclerosing cholangitis in AIDS. CT is the basic and the best modality to guide percutaneous drainage in both the abdomen and the chest, to assess contraindications or to indicate some specific modes; in some cases even plurifocal abscesses can be treated with a percutaneous imaging approach.