The paper presents information on pneumonia (P) patients with features of oxidative stress (OS). Identifying features of OS in patients with P is of interest not only for diagnosis, but also for monitoring of treatment efficiency. We recruited 73 patients with community-acquired P (CAP), previously healthy adults, both males and females with mean age of 68.0 ± 15.2, hospitalised, and 61 healthy control patients matched for age. For quantitative evaluation of lipid peroxidation in CAP patients, the levels of aldehydic lipid peroxidation products like malondialdehyde (MDA) and 4- hydroxynon-2-enal (HNE) were quantified. Furthermore, concentrations of reduced glutathione (GSH) and several antioxidant enzymes and selenium in plasma were determined. In CAP patients, decreased levels of GSH and plasma selenium were observed. Plasma levels of MDA, and HNE did significantly differ between patient and control groups. We also noted reduced activity of antioxidant enzymes, namely, glutation peroxidase and superoxide dismutase. Low antioxidant enzymes activity was associated with a more severe CAP pattern. Both GSH and antioxidant enzymes may serve as markers for inflammation-related OS in CAP patients, and measurement of these biomarkers may be a valid indentifier for its management.