Abstract The paper attempts at providing a comparative analysis of the Grand Duchy of Lithuania and Muscovy during their genesis and early development. Kievan Rus, the predecessor of the Grand Duchy of Lithuania and Muscovy, was not a single political entity; it developed from chiefdoms to city-states that were, in essence, obshchinas (communities). This makes it all the more interesting to understand why the societies with the same roots evolved to become so different. Obviously, what comes to mind is the idea of external influences experienced by various parts of Kievan Rus while the new states were being formed, but the extent and the character of those influences can be understood through comparing these states. Comparing them reveals that they initially shared considerable similarity. It may even be said that there was a common model of state formation in the 13th to 15th centuries. For the purposes of this paper it is labelled a military-service state. It is this quite archaic polity that was the starting point in the progress towards the estates-based state. The paradox of the region is that before either the Grand Duchy of Lithuania or Muscovy could transform into an estates-based state, they both underwent drastic changes: the former became part of the Polish-Lithuanian Commonwealth, essentially a province within it, while the latter was plunged into Ivan the Terrible’s bloody “revolution from the top”, which accelerated the formation of the unique Russian state system based on serfdom.