<p>The physiological role of elements in the human body is profound. Trace elements participate in all biochemical processes, influencing growth and development, fertilization, respiration, hematopoiesis, and immunogenesis. They serve as essential catalysts for various biochemical reactions and metabolism, playing a significant role in adaptation under both normal and pathological conditions. Imbalances in chemical elements—manifesting as either deficiency or excess—can lead to the development of various pathologies, reduced immunity, impaired quality of life, and an increased risk of chronic diseases. Assessing the concentration of chemical elements is a fundamental issue in studying the impact of macro- and microelement deficiency, excess, or redistribution on human health. The diagnostics of microelementoses primarily involves the quantitative determination of elements in human biosubstrates. Modern research requires methods characterized by high sensitivity, precision, and reproducibility, as well as the capability for simultaneous multi-element analysis. One such method is Neutron Activation Analysis (NAA). The relevance of this study is driven by the need to further explore the applications of NAA in evaluating the trace element status of patients and identifying diagnostically significant indicators, specifically through the analysis of blood and hair in children with nosocomial pneumonia.</p>