The aim of the research was to assess the economic, educational and cultural predictors of the TIMSS 2003 science test results in Lithuania and Estonia. The data for the research were received from the TIMSS 2003 User Guide for the International Database. The Spearman rank correlation coefficients, calculated on the students' level and the schools level for both countries, revealed the following predictors. The characteristics of students' socio-economic status were the most powerful predictor of their TIMSS 2003 science score. Books and computers at students' homes were related to their science score. The students' motivation was also a good predictor of their science score, especially on the individual level. The relation of the time-factor to achievement was not very clear. The time spent for homework had no relation to the score in Lithuania and even reduced the science score in Estonia. The parents' educational level was a predictor of the TIMSS 2003 science score in both countries. The parents' native land was important in Estonia but not in Lithuania. The predictors of the TIMSS 2003 science score were concordant with the predictors of the TIMSS 2003 mathematics study and other TIMSS studies: However, some questions remained still unanswered. (Contains 4 tables.)