Pneumocystis jirovecii is a leading cause of opportunistic infections among the immune compromised. During the 1980s, attention focused on patients with HIV, however, with the advent of anti-retroviral therapy, we wished to revisit the question of underlying diseases associated with Pneumocystis pneumonia in children. We identified 80 cases from 1986 to 2006 and performed a retrospective chart review to identify clinical characteristics for each of the cases. HIV was the single most common associated underlying condition seen in this cohort, accounting for 39% of the cases overall, however, it was seen in just 15% of the cases since 1998. Transplant recipients and oncology patients together comprised another 39% of the cases, with 9% of cases attributed to primary immune deficiency and another 9% of cases associated with less well-recognized causes of susceptibility. This study documents the ongoing need for vigilance to diagnose Pneumocystis pneumonia in less well-recognized clinical scenarios. Pediatr Pulmonol. 2012; 47:510516. (c) 2011 Wiley Periodicals, Inc.