The growing processes of the socio-economic inequality resulting from the neoliberal political model are evident in large Spanish cities, with a spatial dimension that allows us to visualise its contradictions with great clarity. These social contradictions are particularly marked among the most vulnerable and foreign population groups. For this reason, the study of the spaces and services termed Social Infrastructures (SI), as facilities which favour social integration and cohesion in the city, is of special importance. Our study addresses the distribution of SI in the Spanish cities of Madrid and Barcelona, their relationship with the level of vulnerability in the neighbourhoods and the distribution of the Spanish and foreign population in a novel way, by creating a synthetic SI index and using a non-hierarchical clustering method. Our results show two completely different city models: in Barcelona, SI are distributed following the criterion of socio-territorial equity, while in Madrid, there is a greater presence of SI in the wealthier areas. This leads us to reflect on the social and political implications of our results in both cities.