Pulmonary infections in children with acquired immunodeficiency syndrome are very common. The lung, having a very important immunological function (because in it a very important part of the secretory immunological system is present), is one of the more involved apparatus in the course of AIDS. We report 4 cases of pulmonary disease (one case of Cytomegalovirus pneumonia, one case of Pneumocystis Carinii pneumonia, and two cases of interstitial lymphoid pneumonia) found in HIV positive children followed at the 5th Pediatric Department - Regional Center, Milan.