A partir da construción de índices analízase o diferente grao de exercicio dascompetencias normativas sobre tributos cedidos nas CCAA de réxime común. Ametodoloxía empregada permite identificar diferenzas existentes entre rexións conrespecto á repercusión ou impacto do exercicio da capacidade normativa sobre osbeneficios fiscais e, asemade, permite analizar a estabilidade da representatividade dasfiguras tributarias no período de estudo 2012-2014. As análises indican que as CCAArealizaron un uso intenso malia que dispar da capacidade normativa cedida, pero que esteexercicio non altera substancialmente a súa estrutura de ingresos, polo que poucocontribúe á configuración dunha facenda autonómica propia. In this paper several indexes are designed with the purpose of assessing theexisting differences between the Autonomous Communities of Spain as far as exercisingtheir assigned regulatory capacity on taxes. The methodology used in the analysis allowsthe identification of differences between regions in terms of the impact of the exercise ofregulatory capacity on tax benefits and it also allows the analysis of the stability of therepresentativeness of different taxes throughout the period 2012- 2014. The resultsindicate that the Spanish Autonomous Communities have made an intensive but unevenuse of the exercise of their regulatory capacity, and that this exercise does notsubstantially alter the configuration of their revenue.