PP-31-175 Background/Aims: In recent decades, the countries after transition experienced rapid socioeconomic differentiation. Most vulnerable groups appear in lower socioeconomic position, described by lower education, occupation, and income. The objective of our study was to investigate the differences in congenital heart malformations' risk among socioeconomic groups in Kaunas, the second largest city in Lithuania. Methods: We conducted the population-based case-control study of newborns in Kaunas in 1999–2005. We compared 198 cases of congenital heart malformations with 643 controls with regard to information on socioeconomic status, reproductive and medical history, etc obtained by questionnaire. We performed the logistic regression analysis for the calculations of odds ratio (OR) for families in different socioeconomic positions, estimated by education and occupation, adjusting for age, marital status, medical history, occupational chemical and residential air pollution exposures. Results: Our results indicated that socioeconomic position described as parental blue-collar occupations and maternal professional comprehensive education, and blue-collar occupations showed the highest risk for congenital heart malformations (adjusted OR = 3.68, 95% confidence interval [CI]: 1.05–12.88) as compared to the socioeconomic position described as parental white-collar occupations, maternal professional comprehensive education, and white-collar occupations. The adjusted OR for socioeconomic position described as parental blue-collar occupations and maternal incomplete and complete secondary education and blue-collar occupations was 2.70, 95% CI: 1.02–7.11. While socioeconomic position described as parental professional occupations and maternal university education and professional occupations showed decreased risk (OR = 0.36, 95% CI: 0.12–1.03). Conclusion: The risk of congenital heart malformations was associated with socioeconomic position in Lithuania, the country after transition.