This paper aims to analyse the space and time distribution of the infant mortality rate (IMR) at municipality level in Colombia before and after conferring greater responsibilities to the municipalities for the administration of the local health care systems. Using special econometrics, we find that there is a geographical concentration of IMR persisting over time and defining two groups of municipalities with mortality levels that oppose each other. Additionally, IMR distribution is found to depend on local and neighbouring factors. We conclude that after 18 years of decentralization, differences among municipalities in terms of IMR increased. Decentralization policies’ designs should include the municipalities’ development levels as well as the neighbouring area context in order to improve the results expected from decentralization.