As an important achievement of the modern international law, the Inter-American and European systems for the protection of human rights, have implemented subsidiary mechanisms of guarantee in order to remedy irregular situations involving human rights at a national level. The Inter-American Court and the European Tribunal, as jurisdictional organs in each system, have played a prominent role in the consolidation of the systems. However, although both systems share the same nature, object and purposes, significant differences arise regarding the operation of the mechanism of guarantee.Consequently, a comparative approach of the organization and activity of both courts (Inter-American and European), the nature and execution of their sentences, and the scope of reparations in each jurisdiction, allows us to find key factors to analyze the issue of their effectiveness.