This work develops and estimates a structural model for inflation in open economies. The model nests the standard New-Keynesian Phillips Curve (NKPC) and the hybrid curve of Gali and Gertler (1999) as particular cases. Two sets of estimates were generated for the Brazilian economy, treated at first as a closed economy and afterwards as a small open economy. In line with recent literature, the model presents inflation inertia and considers a marginal cost measure as the relevant indicator for inflation. Some of the findings can be summarized as follows: (i) Brazil, when treated as a closed economy, shows a considerably higher degree of nominal stickiness than United States and Europe, the same occurs with the level of indexation; (ii) In open economy with indexation, the acceleration of the nominal exchange rate together with external inflation affects consumer inflation, being this effect amplified by the economy s openness; (iii) The direct impact of the variables related to the economy s openness on inflation is small, with the sum of its coeficients close to zero; (iv) However, the indirect impact is significant since it consistently changes the weights associated with lagged inflation and future inflation expectation.