The purpose of this study was to assess an impact of prenatal exposure to fine particles (PM2.5) on the risk of developing respiratory symptoms in early childhood. The study was carried out in a cohort of 465 newborns in Krakow (Poland) who have been followed over the first two years of life. The children exposed to medium level of PM2.5 (>35.3?53.4 µg/m³) had 13% more wheezing days (IRR = 1.13; 95% CI: 1.03-1.23), and those exposed to higher PM2.5 (>53.4 µg/m³) had on average 62% more wheezing days (IRR = 1.62; 95% CI: 1.42-1.86) compared with the low exposure group (≤35.3 µg/m³). The presence of moulds in the household (IRR = 1.13; 95% CI: 1.03-1.24), parity (IRR = 1.18; 95% CI: 1.10-1.28), and maternal atopy (IRR = 1.45; 95% CI: 1.28-1.63) were also significantly associated with the number of wheezing days. Children only exposed to higher PM2.5 (>53.4 µg/m³) had significantly more days with difficult breathing (IRR = 1.54; 95% CI: 1.34-1.78). Since that prenatal exposure to fine particles increases burden of respiratory symptoms among infants and young children the current PM2.5 health air quality guidelines may be too high to protect the sensitive subgroups of population.