HIV infection was first described in a child in 1982. The main route of transmission is mother-to-child, which can occur during pregnancy, perinatally, or through breastfeeding. Preventive strategies are recommended in Poland to minimise the risk of vertical transmission. However, delayed diagnosis still occurs in some HIV-positive individuals. The study presents cases of children with late diagnosis of vertical HIV infection with atypical manifestations. The first case describes a patient presenting with hemophagocytic syndrome, the second with Kawasaki disease, and the third with chronic lung disease. In all cases, HIV diagnosis was delayed due to atypical clinical presentations and prolonged diagnostic process. The diagnosis of mother-to-child HIV transmission in older children is a serious health concern, often associated with advanced, potentially life-threatening stages of the disease. Timely diagnosis and appropriate antiretroviral therapy can significantly improve outcomes. Paediatricians should remain alert to atypical presentation of HIV infection.