Children with congenital heart disease (CHD) have a predisposition to suffer from respiratory tract infections, such as bronchopneumonia (BP). In this study we investigated the characterization of lymphocyte subsets and regulatory T cells (Tregs) in these children. The frequencies of lymphocyte subsets and regulatory T cells were detected in peripheral blood of 400 children patients [100 with BP only, 100 with BP and CHD (BPCHD), 100 with BP and heart failure (BPHF), 100 healthy volunteers] by using three-color flow cytometry. In BPHF and BPCHD groups, lymphocyte subsets characterization of patients was analogous, with lower levels of CD3+, CD3+CD4+, CD3+CD8+, and CD4+/CD8+ ratio but higher levels of CD19+ and CD3–CD16+CD56+ in comparison to BP patients. The differences of the frequencies of CD4+CD25+CD127– T-cells in the four groups were not statistically significant. It was concluded that the cellular immunity function of children with CHD was vulnerable to being damaged after having suffered from BP when compared with the children without CHD, which might be associated with blood circulation difficulties in the majority of children with CHD.