Background <p>In Slovakia, several tens of thousands of persons live in extremely poor living conditions in segregated Roma settlements. We can hardly find populations with such a short life expectancy and a high risk of death in infancy anywhere in Europe. The inadequate infrastructure, catastrophic housing conditions, deteriorated environmental quality, high unemployment and dependence on social transfers in combination with social and geographical segregation or negative behavioral aspects markedly affect their health status and mortality rates. Despite this, only little attention has hitherto been paid to the issues of health mortality, particularly infant mortality, among individuals from this environment. Above all, there is a lack of more comprehensive research that would not only empirically express the mortality of the youngest children and identify its developmental tendencies, but also examine the internal − demographic reasons for this state.</p> Methods <p>The study attempts to fill this gap through cohort-based infant mortality tables, using one- and multidimensional decomposition for the period 1993–2022 for case of marginalized communities mostly in Eastern Slovakia.</p> Results <p>Infant mortality tables corroborated not only the persistence of differences, but also the divergence of mortality compared to the non-Roma population in the country, namely classified by days, weeks and months of the infant’s life. The original one- and multidimensional decomposition of interval life expectancy from birth to the first year of life confirmed a poor situation in the post-neonatal age.</p> Conclusions <p>The above results rise from higher death rates from congenital malformations, deformations and chromosomal abnormalities, as well as from respiratory and infectious diseases. A differential analysis also proved that the level of infant mortality in the selected municipalities was closely related to birth weight. By contrast, the mother’s marital status did not manifest as a differentiating factor.</p>