Male premature mortality in Eastern Europe has been a major public health issue for decades. However, existing knowledge is mainly based on national-level data or large regions within one country. Little is known about mortality variations across smaller geographical units, especially about mortality patterns crossing national boundaries. We aim at exploring spatial patterns of adult cause-specific mortality at the district level across four post-communist countries: Belarus, Lithuania, Poland, and Russia. We assess geographical mortality variation across the districts of all four countries focusing on cross-border continuities and variations within each country. Our results suggest the existence of a mortality gradient from the North-West of Russia to the South of Poland. It shows no discontinuity at the border between Belarus and Russia but a clear divide at the border between Belarus and Poland. Mortality gradients are more pronounced within national populations. Among all countries Russia exhibits the highest regional disparities.