This document discusses the different structural factors which could contribute to inflation persis-tence, and evaluates alternative ways to measure it. Using the "best" methodologies, it presents the evolution of persistence both for the level and the gap of inflation in Colombia in 1990-2010 using a regime switching model and a Kalman filter. The adoption of inflation targeting in 1999 produced an important reduction in mean and variance but has not significantly modified the persistence of inflation.