Pentraxin 3 (PTX3) is a multifunctional acute phase protein belonging to the family of long pentraxins, which is synthesised in numerous cells of the body under the influence of proinflammatory factors and locally at the site of inflammation. Under physiological conditions, PTX3 is stored in neutrophil granules, where there is a constant pool of glycoproteins. Increased pentraxin 3 levels in blood serum are observed as early as 1 hour after a damaging stimulus. Elevation of PTX3 serum levels can be used to diagnose fertility disorders in women as well as in pregnancy pathology, women at risk of pre-eclampsia, gestational diabetes, premature rupture of membrane and preterm delivery. The biological function of PTX3 is not fully understood, especially in the population of newborns and children. So far, no reference values for PTX3 levels in newborns and children have been developed. This protein can be used as a marker of pulmonary hypertension in newborns as well as to assess the degree of respiratory failure in premature infants. In older children, it is useful in the assessment of the severity of meningococcal disease and sepsis as well as in the treatment of childhood asthma. There are studies available in which blood levels of PTX3 significantly correlate with the severity of kidney damage in Henoch–Schönlein macular degeneration in children, and the evaluation of this protein in urine is used to detect renal parenchymal destruction after pyelonephritis.