We analyse the impact of social capital on the willingness to migrate in 28 post-communist and five western European comparator countries using the Life in Transition Survey. We find substantially lower levels of professional social capital among the older cohorts in post-communist than in the comparator countries. In addition, differences in endowments with professional social capital between the post-communist and comparator countries explain 1.5 to 3.9 percentage points of the total 4.0 to 17.0 percentage points difference in the willingness to migrate between the two country groups. Differences in local social capital, by contrast, contribute only little to explaining these differences. Furthermore, the robust positive relationship between the willingness to migrate and professional social capital is mainly due to a strong correlation between these variables among the young in all country groups. We therefore argue that future research should focus on explaining differences in the impact of social capital on migration decisions of different age groups.