Democratic centralism was the Leninist-Bolshevik pyramidal model of internal organization in operation in all communist parties for most of the 20th century. Thus far, the question of whether it functioned consistently across the non-ruling parties has not been addressed explicitly or systematically. This article examines the implementation of this essential internal dynamic in a French and an Italian communist party federation in the early postwar period. Drawing on new personal testimonies from more than 50 informants, and inedita archival evidence, this analysis reveals not only similarities but also clear functional disparities between the two cases.