Serological study of porcine reproductive and respiratory syndrome virus (PRRSV) infection in pigs and wild boars was conducted in Lithuania between 2009 and 2013. Antibody level was measured using a commercial ELISA. The 4.32% (95% CI 3.92-4.72) out of 9856 examined porcine sera were positive for the PRRSV antibodies. The antibodies were detected in 11.82% (95% CI 10.28-13.36) of all investigated serum samples of sows and gilts. As much as 8.2% of serologically positive samples (95% CI 6.83-9.57) were determined in the piglets under three months of age. Considerably smaller (P < 0.05) seroprevalence was detected in boars (0.62%) and fattening pigs (1.84%). From 1357 examined sera of wild boar, collected between 2009 and 2013 hunting seasons, 5.38% (95% CI 4.52-8.2) of samples were positive for PRRSV antibodies in 23 locations out of 50 investigated. The analysis of seroprevalence in different age groups of wild boars showed that PRRSV antibodies were detected in all age groups; however, it was significantly higher in adults than in juveniles or subadults and reached up to 10.02% (95% CI 7.39-12.65).