[eng] Most research on tourism seasonality has focused on tourism flows and, to a much lesser extent, on tourism prices. However, up to now no research has been devoted to understanding the relationship between tourism seasonality in quantities and prices. We try to fill this gap with an application to the Spanish hotels during 2008-2017. Provincial data on the seasonality of night stays and prices of Spanish hotels is presented, compared, and correlated. This data analysis inspires a supply-demand framework to jointly explain both kinds of seasonality. We show the usefulness of this framework to first explain the role of hotels' cost and price flexibility in determining the seasonality of night stays and second to encompass in a single framework most of the determinants of the changes of tourism seasonality in quantities and prices, including some determinants seldom considered in the literature.