This work deals with the patronage of the queens-consort and princesses in the Western part of the Iberian Peninsula from a comparative point of view. Its main aim is to analyze the ways of acting common both to Castile and Portugal and, at the same time, to examine the differences between both kingdoms in the period that covers the late 14th century and the beginnings of the 16th century, corresponding to the rule of the Trastamara and the Avis dynasties. The analysis of their sponsorship shows a wide variety of themes inside the prevalence of religious subjects. The cultural initiatives of these noble women must be considered in a context where monarchy was highly exalted, a feature characteristic of the origins of the Modern State at the end of the Middle Ages and the Renaissance period.