Background: Highly active antiretroviral therapy (HARRT) has dramatically changed the prevalence of PCP however it depends on the ability to diagnose and treat HIV with ARV of each nations. Objective: Identify the prevalence of PCP in HIV-infected children with pneumonia in Vietnam National Hospital of Pediatrics (VNHP) and describe the clinical, sub-clinical characteristics and treatment of those cases. Subject and methods: Cross-sectional study of HIV-infected children with PCP among 79 cases with pneumonia treated in Infectious Diseases Department and Intensive Care Unit in VNHP from January 2011 to January 2013. Results: The prevalence of PCP among HIV-infected children with pneumonia is 13.9 percent. 72.7 percent children have co-infection with either virus, fungus or bacteria. 90.9 percent have CD4 counts below 20 percent. The most common symptoms in PCP are cough (81.8 percent), dyspnea (72.7 percent), cyanosis (72.7 percent), pathological crackle in lungs (90.9 percent), oxygen saturation below 90 percent (72.7 percent). Chest radiographs usually show simple or combination interstitial lesions (81.8 percent) with 2/11 cases (18.2 percent) having total opacification on both lungs. Conclusion: PCP among HIV-infected children with pneumonia (prevalence 13.9 percent) usually have co-infection and severe immunodeficiency. It is necessary to pay attention to PCP while treating and providing prophylaxis for AIDS children with pneumania in Vietnam.