Low birth weight (LBW) is a result of preterm birth or intrauterine growth retardation, and in both cases is the strongest single factor associated with perinatal and neonatal mortality. It is considered that socioeconomic factors, as well as mothers bad habits, play the most significant role in the development of LBW, which explains notable number of researches focused on this particular problem. The aim of this study was to characterize socioeconomic factors, as well as smoking habits of the mothers, and their connection with LBW. The questionnaire was carried out among mothers of 2 years old children (n = 956), born after 37 gestational weeks. The characteristics of mothers who had children with LBW, defined as < 2,500 g, (n = 50), were matched with the characteristices of mothers who had children > or = 2,500 g, (n = 906). For defining risk factors, and protective factors as well, we used univariant and multivariant logistic modeles. As significant risk factors for LBW in an univariant model we had education level of the mothers, smoking during pregnancy, smoking before pregnancy, the number of daily cigarettes, the number of cigarettes used during pregnancy, paternal earnings and socioeconomic factors. In a multivariant model the most significant factors were socioeconomic factors, education level of the mothers, paternal earnings and mothers smoking during pregnancy. Smoking during pregnancy and socioeconomic factors have great influence on LBW. Future studies should be carried out in different social groups, with the intention to define their influence on LBW and reproduction, as well. This should be the proper way of adequate health breeding planning for giving up smoking, the prevention of bad habits and melioration of mothers and children health, as the most vulnerable population.