The aim of this work is to assess the use of Facebook as a social marketing tool by organizations dealing with children with cancer disease. The theoretical part contains information about non-governmental organizations, the characteristics of selected foundations from Spain and the function of social media. The empirical part of the work was carried out in October and November 2018 during the author's stay in Spain. Posts published by three Spanish foundations Aladina from Madrid, Aspanion from Valencia and Afanoc from Barcelona have been analysed. They are the three largest cities in Spain, which is why the foundations were chosen from them. The analysis included Facebook tools, which were the most used by foundations, then the type of published content and at the end was selected the best post. The results show that the main posts of the organizations are related to fundraising, while the most used tools were photos.