While experiencing one of the most extreme population declines in the world, quite many infants are born to teenage mothers in Lithuania. Adolescent fertility rate (AFR) in Lithuania is up to four times higher compared to the Northern and Western European countries. However, there is a great regional differentiation of AFR on the low spatial level in the country, where this rate is significantly higher in the peripheral rural regions, but such phenomenon is almost absent in the major cities. The aim of our research is to investigate the regional differentiation of AFR in Lithuania and to identify individual as well as regional characteristics determining it. This study uses individual-level Lithuanian census data from 2001 and 2011. First, we analyse the patterns of regional differentiation of AFR over time at the detailed spatial level. Second, we use binary logistic regression modelling to gain an understanding of which individual characteristics and the attributes of the socio-economic environment contributes most to the increased likelihood of childbirth in adolescence. Our primary results show that individual characteristics play much bigger role than socio-economic environment. The results therefore also suggest that the role of sexual education must be strengthened. The research is funded from the project “Spatial differentiation of adolescent fertility in Lithuania: socioeconomic environment, the role of sexual education and individual experiences” (financed by the Lithuanian Research Council, contract No. S-MIP-17-115).@en